Question 135287
Let x=amount of time needed for both working together
One riviter works at the rate of 1/12 job per day

The second riviter works at the rate of 1/16 job per day

Together they work at the rate of 1/12  +  1/16 job per day, or

4/48  + 3/48 = 7/48 of the job per day.  So our equation to solve is:

(7/48)x=1  (1 job, that is)  multiply each side by 48

7x=48  divide both sides by 7

x=6 6/7 days or 6.8571 days

Hope this helps  -----ptaylor