Answer:
I don't know much about linear regression, but I would say the answer is 15.25. The x-value number closest to 75 is 77, and the corresponding y value is 16.5. Since there is a big difference between the other answers and 16.5, you can estimate and conclude that 15.25 is probably the answer. Sorry if this doesn't help much since I wasn't able to explain the correct way they asked you to do the problem. :/