Answer: The correct answer is C.
Hi, here you can see that the forces are in the same line, but they are opposite to each other.
So if you want to obtain the net force, you must do a sum of all the forces. in this case we have 250 N to east, and 150 N to west, the first step will be have the same axis, in this case West is the opposite of East (tooking east as the positive direction here), then 150N west = -150N to east.
Now doing the sum we obtain Ft = F1 + F2 = 250 N - 150 N = 100N to the east.
so the correct answer is C.