Question 1112513
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<pre>
Let x be an amount invested at 5%, in dollars.

Then the amount invested at 8% is the rest (12000-x) dollars.



Your basic equation is THIS:


<U>interest</U> + <U>interest</U>       = <U>total interest</U>


0.05*x   + 0.08*(12000-x) = 840.


0.05x + 0.08*12000 - 0.08x = 840


-0.03x = 840 - 0.08*12000 = -120  ====>  x = {{{(-120)/(-0.03)}}} = 4000.


<U>Answer</U>.  $4000 was invested at 5%  and the rest  12000 - 4000 = 8000 dollars was invested at 8%.


<U>Check</U>.   0.05*4000 + 0.08*8000 =  840 dollars.   ! Correct !
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To see many other similar solved problems on investment, &nbsp;look into the lesson

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/coordinate/lessons/Using-systems-of-equations-to-solve-problems-on-investment.lesson>Using systems of equations to solve problems on investment</A>

in this site.


You will find there different approaches &nbsp;(using one equation or a system of two equations in two unknowns), &nbsp;as well as 
different methods of solution to the equations &nbsp;(Substitution, &nbsp;Elimination).


Also, &nbsp;you have this free of charge online textbook in ALGEBRA-I in this site

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson>ALGEBRA-I - YOUR ONLINE TEXTBOOK</A>.


The referred lesson is the part of this online textbook under the topic &nbsp;"<U>Systems of two linear equations in two unknowns</U>".



Save the link to this online textbook together with its description


Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson


to your archive and use it when it is needed.