What is the length of YZ?

28.6 units

Step-by-step explanation:

44/36=35/YZ

44 YZ = 35*36

44 YZ = 1260

YZ = 28.6 units

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