This strategy works because if you subtract one number from another the sum of the two numbers should be the that is being subtracted from. (In this case, it's 200)
In this item, we are tasked to determine the calculation that can be done in order to determine the length or width of the painted mural in each striped area. This can be done by dividing the total length by the number of stripes as shown in the equation below.
Length per stripe = Total length / number of stripes
Length per stripe = 15 yards / 96 stripes
= 0.15625 yard/stripe