Explanation:
I cannot draw here, but I can explain things.
x = number of hours grading.
we have 2 functions for the grading progress : one for Prof. Maynard, one for her TA.
Maynard(x) = 8x + 20
as she can grade 8 assignments per hour and has already finished 20.
TA(x) = 10x
now, the description says that they will be finished, when they have graded the same number of assignments.
so,
8x + 20 = 10x
20 = 2x
x = 20/2 = 10 hours
after 10 hours they will each have graded 10×10 = 100 (or 8×10 + 20 = 100) assignments.
you graph each line by finding 2 points. one e.g. for x = 0, and one for e.g. x = 10. you calculate the y value for each of these x values. at each (x, y) you mark the point. and then you just connect the 2 points for every line (and extend the line beyond the points).
the solution is the point, where both lines intersect.