The sum of the interior angles of a hexagon is 720 degrees, and there are two right angles. The sum of the known angles is 573, so 720-573 is 147.
Pick c.
The pattern having the fastest growth rate is :
8x - 4y = 8
-4y = -8x + 8
y = -8x/-4 + 8/-4
y = 2x - 2, comparing to y = mx + c, slope m = 2
Slope = 2.