Question 622177
it takes shawn 18 hours to paint a house.  karen can paint the house in 12 hours.  how long will it take shawn and karen working together to paint the house?
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Let x = time (hours) it takes together
then
x(1/18 + 1/12) = 1
multiplying both sides by (18)(12):
x(12 + 18) = (18)(12)
x(30) = 216
x = 216/30
x = 7.2 hours
or
x = 7 hours and 12 minutes