Final answer:
To find the value of x, we can use the perimeter formula for a rectangle. By expressing one side in terms of x and simplifying the equation, we can solve for x.
Step-by-step explanation:
The perimeter of a rectangle is the sum of all its sides. Let's denote the length of the rectangle as l and the width as w. The formula for the perimeter is P = 2l + 2w. According to the question, the perimeter is 90 inches. So, we can write the equation 2l + 2w = 90. However, we're given that the value of x is unknown, so we need to express one side in terms of x. Since the rectangle has two equal sides, we can write l = x and w = (90 - 2x)/2. Substituting these values into the equation, we get 2x + 2[(90 - 2x)/2] = 90. Simplifying this equation will give us the value of x.