Question 1201382
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The ratio of 20cent coins and 10cent coins was 4:7 respectively. 
After exchanging 8 20cent coins for 10cent coins the ratio became 2:11 . 
How much money did Bob have at first.
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<pre>
At first, there were 4x 20-cent coins and 7x 10-cent coins.


After exchange 8 20-cent coins for 10-cent coins, there were 
(4x-8) 20-cent coins and (7x+16) 10-cent  coins.


Your equation is

    {{{(4x-8)/(7x+16)}}} = {{{2/11}}}.


Solve and find x

    11*(4x-8) = 2*(7x+16)

    44x - 88 = 14x + 32

    44x-14x = 32 + 88

      30x   =    120

        x   =    120/30 = 4.


At first, there were 20*4x + 10*7x  = 80x + 70x = 150x = 150*4 = 600 cents = 6 dollars.    <U>ANSWER</U>
</pre>

Solved.



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It is a standard style which @Theo uses in solving Algebra problems and presenting his solutions: 

he takes the most inappropriate approach and writes a solution in 3-5 times longer than it should be.


He repeats it every day, from month to month.



As soon as he sees my short solution, he considers it as his duty to write his own solution in 3 - 5 times longer.



I can not imagine a person in healthy mind who will read such solutions.