Answer:
b = -9
Step-by-step explanation:
As we go from M(4, 3) to N(7, 12), x increases by 3 and y increases by 9. Thus, the slope of the line segment connecting these two points is m = rise / run = m = 9/3, or just m = 3.
Subbing the coordinates of M into y = mx + b, we get:
3 = 3(4) + b, or 3 = 12 + b, so that b = -9.
