Question 39034
Mr. Coyne has some dimes and quarters. He has twice as many dimes as quarters. The total value of his coins is $8.10. How many dimes does he have? 

Let the number of quarter be "x".
Value of these quarters is 25x cents
The number of dimes is "2x"
Value of these dimes is 10(2x)=20x cents
EQUATION:
value + value = 810 cents
25x+20x=810
45x=810
x=18 (number of quarters)
2x=36 (number of dimes)
Cheers,
Stan H.