Hillary has eleven coins, all dimes and nickels. In total, the coins are worth 75 cents. How many nickels does she have?
0.05N + 0.10 * [11 - N] =0.75, solve for N
N = 7 nickels
11 - 7 = 4 dimes
[7 x 0.05] + [4 x 0.10] =0.75 or 75 cents.
