We are given that T = test score, and x = # of hours studied. We are given the same information in numbers:
T = 90
x = 6
y = ?
We need to figure out y in terms of k. Let's set up what we know:


Let's multiply both sides by y to get rid of it on the right side:

Now, let's divide by 90 on both sides to get rid of it from the left side (and solve for y):

Your answer is A! If any part didn't make sense, you know where to reach me.