SOLUTION: Twin brothers, Billy and Bobby, can mow their grandparent's lawn together in 117 minutes. Billy could mow the lawn by himself in 40 minutes less time that it would take Bobby. How

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Question 904053: Twin brothers, Billy and Bobby, can mow their grandparent's lawn together in 117 minutes. Billy could mow the lawn by himself in 40 minutes less time that it would take Bobby. How long would it take Bobby to mow the lawn by himself?
Answer by josgarithmetic(39616) About Me  (Show Source):
You can put this solution on YOUR website!
Form expressions for each rate in LAWNS per MINUTE. Let x = time for Bobby to mow lawn himself, alone.

RATES
Billy, 1%2F%28x-40%29
Bobby, 1%2Fx
Billy & Bobby Together, 1%2F117

Rate of both together is the sum of their individual rates:
highlight%281%2F%28x-40%29%2B1%2Fx=1%2F117%29;
so just solve for x.