Question 319876
    Jack usually mows his lawn in 3 hours. Marilyn can mow the same yard in 6 hours. How much time would it take them to mow the lawn together? They could mow the lawn in how many hours if they worked together. 
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Let h = hours it takes if they worked together
then
h(1/3 + 1/6) = 1
multiplying both sides by 18:
h(6 + 3) = 18
9h = 18
h = 2 hours
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The can mow the lawn in 2 hours if they work together.