A bank teller knows she received 34 dimes and nickels combined from a customer. If the change totaled $2.05 how many nickels and dimes did she receive
10 d + 5 n = 205
d + n = 34 so d = 34 - n
10 (34-n) + 5 n = 205
340 - 205 = 10 n - 5n
135 = 5 n
n = 27
d = 34 - 27 = 7