1) What is the perimeter if the width is 50 meters?
You are told that the formula for the perimeter is: P=2*l+2*w. You are also told that the length, l = 100m. To find the perimeter if the width, w = 50m, just plug the numbers into the formula and solve for P:
P=2*l+2*w
P=2(100) + 2(50)
P = 200 +100
P = 300m
2) What is the width if the perimeter is 344 meters?
Now you're told the perimeter, P = 344m, and asked to find the width. Use the same formula, P=2*l+2*w. The length is still l=100m:
P=2*l+2*w
344 = 2(100) + 2w
344 = 200 + 2w
144 = 2w
w = 72m
---------
Answer:
1) Perimeter = 300 meters
2) Width = 72 meters