Question 1203641
.


It is quite obvious that two unknowns are enough to solve the problem.


Two tutors, @ankor@dixie-net.com and @Theo proved it by providing complete solutions
using two variables.


Then suddenly @josgarithmetic comes with his idea to use 4 unknowns,
and writes the system of three equations for it, proposing the student to use it.


Obviously, this his idea is not very smart (if do not say more).


Also, it is obvious that it is NOT POSSIBLE to find 4 unknowns from the system of three equations.


Therefore, my advise to the reader is to ignore the post by @josgarithmetic, 
as if you've never seen it - for safety of your mind.



Below is my solution using only one unknown.



<pre>
Let x be the number of goldfish, initially.

Then the number of guppies was (x+35), initially.


Adter adding, there are {{{(8/5)x}}} of goldfish and {{{(7/6)*(x+35)}}} of guppies.


The total is 193 now

    {{{(8/5)x}}} + {{{(7/6)*(x+35)}}} = 193.


To solve this equation, multiply the terms by 30.  You will get

    48x + 35(x+35) = 30*193.


Simplify it further

    48x + 35x = 30*193 - 35*35

       83x    =     4565

         x    =     4565/83 = 55.


So, initially there were 55 goldfish in the tank and (55+35) = 90 guppies.


At the end, there is {{{(7/6)*90}}} = 105 guppies in the tank.


<U>ANSWER</U>.  There are 105 guppies in the tank at the end.
</pre>

Solved.