You can do one-half of a job in an hour. your friend can do one-third of the same job in an hour. how long will it take to do the job if you work together. write your answer as a decimal.

That means you can do the whole job in two hours and he can do it in three. The set up then becomes
t/2 + t/3 = 1  and then 
Multiply by 6 and get
3t + 2t = 6
5t = 6
t = 6/5 = 1.2 hours = 1 hour 12 minutes