The scale factor is 1.5 because:
9 x 1.5 = 13.5
5 x 1.5 = 7.5
7s + 20 = 4s -13
7s - 4s = -13 -20
3s = -33
s = -33/3
s = -11
Let x the subject of the equation in x-2y=-10 this make it x=2y-10 substitute this in the first equation. 3(2y-10)-2y=-6 solve for y, y=6. substitute y in any of the original equations to get x x= 2
Total length of boards needed = 2000*3.5 = 7,000.
Total number of 8' boards needed = 7000/8 = 875 answer
4ab / 8c
a=8
b=4
c=12
4 x 8 x 4 / 8 x 12 = 192
Hope this helped!!!