In order to find the perimeter, we need to have the length and the width. We are told that the area of the rectangle is 42. We will use that in the area formula, length times width, to solve for w. 42 = 7w so w = 6. The length is 7 and the width is 6. The perimeter formula for a rectangle is P = 2L + 2W. We have both the length and the width now, so we fill in accordingly. P = 2(7) + 2(6). And P=14+12. The perimeter then is 26 inches.