Answer:
Wood family: 35 hours
Roberts family: 25 hours
Step-by-step explanation:
Let w represent the number of hours the Woods family ran their sprinkler. Then 60-w is the number of hours the Roberts family ran theirs. The total water usage (in liters) was ...
25w + 15(60-w) = 1250
10w = 350
w = 35 . . . . . . Wood family time (hours)
60-w = 25 . . . Roberts family time (hours)
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Check
(35 h)·(25 L/h) + (25 h)·(15 L/h) = 875 L + 375 L = 1250 L . . . . answer checks OK