Question 928114
let x be the number of nickels and y be the number dimes, then we have
2x +x +y = 52
.25(2x) + .05x + .10y = 8.20
solve first equation for y
y = 52 -3x
substitute for y in second equation
.25(2x) + .05x + .10(52-3x) = 8.20
.50x + .05x + 5.20 - .30x = 8.20
.25x = 3.00
x = 12
therefore,
there are 24 quarters, 12 nickels, 16 dimes
now check the answers
24*.25 + 12*.05 + 16*.10 = 8.20
6.00 + .60 + 1.60 = 8.20
8.20 = 8.20
answer checks  :-)