The perimeter of a rectangle is 56 inches. The length is 4 more than 3 times the width. What is the length of one side of the rectangle

So the width of the rectangle is x. You would write an equation as x + (3x+4) = 56.

You add because you are finding the perimeter. You would simplify the equation down to 4x+4=56. You take the four out by subtracting it on both sides, the four itself and 56. You would be left with 4x=52. You then divide 4x by 4 to cancel out the 4 to have just x and also divide 52 by 4, and you would get 13. Then you substitute all x by 13. Your equation would be 13 + (3 (13) + 4) = 56. You then simplify and get 13+43=56. You then add and get 56=56.