Answer:
Job A is more profitable for nearly 49 months (or 50 months including the first month)
Job B is more profitable after 49 months (or 50 months including the first month).
Explanation:
Let x be the number of months passed after first month
Job A:
$2,000 for the first month with a $300 raise every month thereafter
Function describing this situation:

Job B:
$1,500 for the first month with a 5% raise every month thereafter
Function describing this situation:

Plot both graphs (see attached diagram). The diagram shows that the job A is more profitable for nearly 49 months (or 50 months including the first month) and the job B is more profitable after 49 months (or 50 months including the first month).