Solving a value mixture problem using a system of linear equations

Question

The Gonzalez family and the Simmons family each used their sprinklers last summer. The Gonzalez family's sprinkler was used for 20 hours.The Simmons family's sprinkler was used for 40

 hours. There was a combined total output of 1600L of water. What was the water output rate for each sprinkler if the sum of the two rates was 60L per hour?

Answer 1

40S + 20G = 1600

S+G = 60

S = 60-G

40(60-G) + 20G = 1600

2400 -40G +20G = 1600

20G = 800

G =800/20 = 40 L/hr

S = 60-40 = 20 L/hr

20x40 + 40x20 = 800+800 = 1600