Homework calculus

Question

Part of the proceeds from a garage sale was 355 worth of 5 and 20 bills.if there were 6 more 5 bills than 20 bills,find the number of each denomination

Answer 1

5F + 20T = 355

F=6+T

5(6+T) + 20T = 355

30 + 5T + 20T = 355

25T = 355-30 = 325

T = 325/25 = 13 twenties

F = 19 fives

355 = 5(19) + 20(13) = 95 + 260