Marian can weed a garden in 3 hours. Robin can weed the same garden in 4 hours. how long will the weeding take them if they work together?

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marian can weed 1 garden in 3 hrsmarian can weed 1/3 garden in 1 hr.robin can weed 1 garden in 4 hrsrobin can weed 1/4 garden in 1 hrin 1 hr, robin and marian can weed (1/3 + 1/4) garden  = 7/12 gardenThus, robin and marian weed 7/12 garden in 1 hr.then, robin and marian weed 1 garden in 12/7 hrs.

You just figure out that 1/4 of the job is done in 1 hour, and another 1/3 of the job is done in the same time. so 1/4*1/3 equals 7/12. So 7/12x=1. Then u multiply 12/7 on each side so you get 12/7 as ur answer.