Question 1099859
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Let Q be the number of quarters.

Then the number of nickels and dimes is (42-Q), and the condition says that 

this number (42-Q) is 2 less than Q.


It gives you an equation 

42 - Q = Q - 2,  which implies

2Q = 42 - 2 = 40  and  then  Q = {{{40/2}}} = 20.


So, we have 20 quarters that sum up to 20*25 = 5 dollars.


Taking these 20 quarters away, we have 42-20 = 22 coins that are nickels and dimes and worth 710 - 500 = 210 cents.


If you think one minute on it, you will find the solution MENTALLY: 20 dimes and 2 nickels.



<U>Answer</U>.  20 quarters, 20 dimes and 2 nickels.
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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<U>The key to the solution of this problem is to choose the leading unknown correctly</U>.