I would go with B) 10 because if you look it intercepts the y at 15 and in 1 square it goes up to 25 and so forth which is a 10/1 slope
So in the future use the formula y2-y1/x2-x1. Pick two point usually you want point that fall on a grid line but work with what you have so 45-35 / 3-2 = 10/1
