A sum of money amounting to $4.25 consists of dimes and quarters if there are 26 coins in all how many are quarters

d = dimes

q = quarters

d+q=26 coins

rewrite as d=26-q

0.25q + 0.10d=4.25

0.25q+0.10 (26-q) = 4.25

0.25q+2.6-0.10q=4.25

0.15q=1.65

q=11

d=26-11=15

11*0.25 = 2.75, 15*0.10=1.50, 2.75+1.50=4.25

there are 11 quarters