Question 1111987
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If you don't need to use formal algebra to solve the problem, here is an easy way to get the answer to this kind of problem with a little mental arithmetic.<br>
If all 45 hours of water used had been by the James family, the total water usage would have been 45*30 = 1350L -- 150L short of the actual total.<br>
The Stewart family's sprinkler uses 5L more per hour than the James family's; to get those "extra" 150L of water usage, the number of hours the Stewart family's sprinkler had to be running is 150/5 = 30.<br>
And that leaves 45-30 = 15 hours for the James family's sprinkler.<br>