math
posted by myla .
how many dimes and quarters does jill have if she has $9.90 in dimes and quarters and she has 3 times as many dimes as quarters?

D = 3Q
10D + 25Q = 990
Substitute 3Q for D in second equation and solve for Q. Insert that value into the first equation and solve for D. Check by inserting both values into the second equation.