Answer: Look below :)
Explanation:
I graphed the inequality below:
from that we can see:
a. Points on the line are combinations of US/Mexico minutes he can do where all of his prepaid money will be used, For example, he could do 50 USA minutes and 80 Mexico minutes, and there would be no money left to spend
b. Points above the line are combinations of US/Mexico minutes that will cost him more than the prepaid $50.
c. Points below the line are combinations of US/Mexico minutes that will leave him with money left over from his $50.
I hope this makes sense! ask questions if you have any :)