Solve using system of equations. q=number of quarters and d=number of dimes .25q+.10d=5.50 because the total of dimes and quarters is $5.50 8+d=q because there are 8 more quarters than dimes substitute 8+d for q into the first equation to get .25(8+d)+.10d=5.50 then simplify 2+.35d=5.50 .35d=3.50 d=10 he has 10 dimes