Step-by-step explanation
Let the number of hours Joe worked at the first job be x while the number of hours he worked at the second job be y.
Therefore, since he works 20 hours per week, we can say that

Also, since he made $127 in a week;

Isolate for x in equation one.

Substitute the above in equation 2.

Also,

Answer: Job A= 10 hours
Job B= 10 hours