Posted by Brian on .
jose can complete the job in a hours, and Maria can complete the job in b hours. How long does it take them to complete the job when they work together? I need a formula

Algebra 
Reiny,
Jose's rate = job/a
Maria's rate = job/b
combined rate = job/a + job/b
= job(a+b)/(ab)
combined time = job/combined rate
= job/[job(a+b)/(ab)]
= ab/(a+b)