Question 160575
Let x=amount of time it takes to do the job when they work together
Jerry works at the rate of 1/5 of the job per week
Sam works at the rate of 1/3 of the job per week 

Together they work at the rate of:
1/5 + 1/3=3/15 +5/15=8/15 of the job per week
So, our equation to solve is:
(8/15)x=1 (1 job, that is) multiply each side by 15
8x=15 divide each side by 8
x=1.875 weeks---------------------------ans
Another way:
if x=amount of time it takes to do the job when they work together, then, together, they work at the rate of 1/x job per week, so:
1/5 + 1/3 =1/x  multiply each term by 15x
3x+5x+15
8x=15----same as before

CK
Amount of work that Jerry does in 1.875 weeks plus the amount of work that Sam does in 1.875 weeks has to equal 1 job completed,so:
(1/5)*1.875 + (1/3)*1.875=1
0.375+0.625=1
1=1

Hope this helps---ptaylor