Find the dimensions of a rectangle given its perimeter and one of its side lengths.

The formula for the perimeter of a rectangle is P = 2 * (a + b), where a and b are the side lengths. 1. For P = 156 m and b = 42 m: 2 * (a + 42) = 156 => a + 42 = 78 => a = 78 - 42 = 36 m. Therefore, the dimensions are 36 m and 42 m.