Sprinkler total

Question

The campbell family and the perry family each used sprinkler last summer. The water output rate for the campbell family sprinkler was 35L per hour. The water output for the perry family sprinkler was 15L per hour. The family used their sprinkler for a combined of 55 hours, resulting in a total water output of 1325L. How long was sprinkler used

Answer 1

C is the number of hours for the Campbell family

P is the number of hours for the Perry family

C+P = 55

35C + 15L = 1325

35C + 15 ( 55 - C) = 1325

35C + 825 - 15C = 1325

20C + 825 = 1325

20C = 500

C = 25

This forces P=30