Need on this two column proof for geometry

Arectangular exercise mat has a perimeter of 36 feet the length of the mat is twich the width writeand solve an equation to determine the length in feet. of the mat then find the area in square feet of the mart

Acredit card advertises an annual interest rate of 23%. what is the equivalent monthly interest rate?

Another type of subtraction equation is 16-b=7. explain how you would sole this equation then solve it.