First you need to figure out the slope:
y2-y1/x2-x1=(1+5)/(-5-7)=-1/2
y+5=-1/2(x-7)
y=-1/2x-3/2
Answer:
b) 29π mm²
Step-by-step explanation:

A)24 boards/1 * 47.5 inch/boards * 1 ft/12in = 95 ft.
according to dimensional analysis the answer is 95 ft.
b) 95/8 is approximately 12 so 12 boards are needed.
25.05 in
Perimeter you just add all of the sides together.