answer
5/2
Step-by-step explanation
he needs 17 1/2 = 35/2 meters of fabric to cover both sides
divide by 2 to find the area of fabric to cover one side
area = (35/2) / 2 = 35/4
area = length * width
35/4 = length * width
length is 3 1/2 = 7/2
35/4 = 7/2 * width
width = (35/4) / (7/2)
width = (35*2) / (7*4)
width = 70 / 28
width = 5/2