Answer:
Russell family's sprinkler: 40 hours
Gonzales family's sprinkler: 20 hours
Step-by-step explanation:
Let's call the amount of time the Russell family's sprinkler was on by X, and the Gonzales family's sprinkler by Y.
We can then formulate the equations:
X + Y = 60
X*35 + Y*40 = 2200
We can solve this system multiplying the first equation by 35, and then subtracting the result from the second equation:
35*X + 35*Y = 2100
5*Y = 100
Y = 20
from the first equation:
X + 20 = 60
X = 40
Russell family's sprinkler: 40 hours
Gonzales family's sprinkler: 20 hours