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. the job will take hour(s).

So, you can do 0.5 of the job and your friend can do 0.3 of the job (in one hour)
Working together, you should be able to do 0.7 of the job in 1 hour.

So, let's write it this way:

Now solve for x:
1 * 1 / 0.7
1 / 0.7
x = 1.428571428571429
This can be rounded to 1.43 hours if needed 
The job will take 1.43 hours

The only number less than 8 that can equal 12 would be 6, 36 is the dividend