The length of the rectangular garden is 30 meters. It took 100m of mesh to make a fence around

The length of the rectangular garden is 30 meters. It took 100m of mesh to make a fence around the garden. How wide is the garden?

The grid around the garden is the perimeter of the garden. Since the formula for the perimeter of a rectangle is – P = (a + b) * 2 (where P is the perimeter, a is the length, b is the width), we will derive the formula for finding the width from it.
P = (a + b) * 2 = 2a + 2b
b = (P – 2a) / 2
(100m – 30m * 2) / 2 = (100 – 60) / 2 = 40/2 = 20 (m) – garden width
Answer. The garden is 20 meters wide.