Question 136426
Let x=amount of time it takes A&B to do the job working together
A works at the rate of 1/5 of the job per hour
B works at the rate of 1/8 of the job per hour

Together A & B works at the rate of 1/5+1/8 (LCM is 40)
=8/40 + 5/40=13/40 of the job per hour, so our equation to solve is:

(13/40)x=1 (1 job, that is) multiply each side by 40

13x=40 divide each side by 13

x=3.0769 hours-----------------------time it takes A&B to do the job working together

Hope this helps---ptaylor