I would implore you NOT to even pay attention or look at the other person's attempt to help you. Numerous times on here these people have been SHOWN how to do these

problems and STOP making them so COMPLEX and time-consuming but they NEVER learn! Maybe they consider themselves too old to learn or maybe they're just STUBBORN!

Anyway, this is how this should be done.



Let the amount invested at 10% be T

Then the amount invested at 11% is, T + 300

And so, amount invested at 12% = 2,900 - (T + T + 300) = 2,900 - 2T - 300 = 2,600 - 2T

We now get: .1T + .11(T + 300) + .12(2,600 - 2T) = 324

.1T + .11T + 33 + 312 - .24T = 324

.1T + .11T - .24T = 324 - 345

- .03T = - 21

Amount invested at 10%, or 

You should now be able to determine the amounts invested at the other rates.

That's IT!! Nothing as COMPLEX and TIME-CONSUMING as one of the NOVELISTS makes it seem!! 

Answer by josgarithmetic(39617)   (Show Source): You can put this solution on YOUR website!
 
RATE%      VARIABLE OR QUANT.              EARN
10               x                         0.1x
11               x+300                     0.11(x+300)
12              2900-x-x-300=2600-2x       0.12(2600-2x)
TOTALS          2900                       324




Setup and solve the equation  .

Then evaluate the other two quantities. 

Answer by ikleyn(52781)   (Show Source): You can put this solution on YOUR website!
 .





This problem can be solved using ONE single equation for ONLY ONE unknown, as the tutor @MathTherapy showed tou.





Moreover, this problem is designed, intended and expected to be solved in this way. 

It is SPECIALLY INTENDED to teach the student this method.





The complications, made by @josmicely, are absolutely unjustified and guide the student in the way to NOWHERE.





This problem is intended for 7-th grade middle school students, who did not study systems of equations yet.





@josmicely, I explained this doctrine, probably, 30 times in this forum, and I am VERY SURPRISED that my explanations 

passed out of you.







-----------------

Comment from student: answering a question does not mean criticizing other people’s ways of solving math, 

nor is it agreeing with someone else’s solution. you should have to solve it yourself. you are very unhelpful. 

stop answering questions if you are not going to do it properly.

-----------------







My response : 





1.  Why do you think your opinion is right ?

    I think, in opposite, that in the given concrete case MY OPINION IS RIGHT.



2.  Since my knowledge in Math (and my understanding on how to TEACH Math) is 1000 times greater than yours, you better 

    listen to me attentively.


3. The best response from your side, when I write to you, is to say "THANKS".

    Any other response/answer from your side is WRONG.


4.  At this forum, half of so named (so called) "tutors" have no enough qualification to be real tutors.

    And they produce a huge amount incorrect solutions EVERY day.

    Therefore, I perform here some functions of a police officer and a cleaner to support some order at the forum.

    It means that, in addition to my numerous own solutions, I am cleaning after that "tutors", by re-writing their "solutions" every day.

    Without it, the forum will quickly become a GARBAGE BOX and a TRASH SECTION.


    Can you imagine some kind of democracy without police officers ? - It will quickly degenerate to  сhaos.

    So, supporting the order here, I work for you, by the way and in particular (!)

    Do you understand it ?


5.  Regarding your complains that you do not understand my solutions, could you refer to such my posts ?

    I, in opposite, think, that my solutions and explanations are OF THE BEST at this forum.


    So, give me a reference, and I am ready to discuss YOUR PROBLEMS with you.


     I am looking forward to hear from you.


                           Have a nice day (!)


--------------


P.S.  I also understand that some visitors at the forum may not understand a solution to any arbitrary problem -

      even although a whole army of professors will explain them - people are different.


      Keeping it in mind, I work here partly for ETERNITY - for future generations of students,

      who may scoop knowledge from my solutions/posts in archive.


      It means, that not only you, the visitor, are in the focus of my attention, but future generations of students, too.


      In other words, if even you do not understand some solution - it is all right - the other generations students will learn from it (!)




 

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