Question 175617
Call the number of five's F.  Then there are 3F one-dollar bills and (1/2)F ten dollar bills.  The dollar amount of fives is 5F, one's is 1(3)F and tens is 10(1/2)F. So
5F + 1(3)F + 10(1/2)F = 260
5F + 3F + 5F = 260
13F = 260
F = 20

20 Fives
60 Ones
10 Tens