Find the width of rectangle given the perimeter

The length of a rectangle is three more than twice the width. The perimeter is 78 centimeters. What is the width in centimeters of the rectangle?

x = width
2x + 3 = length   {the length is 3 more than twice the width} 

Perimeter of a rectangle is 2(width) + 2(length} 

2x + 2(2x + 3) = 78   {substituted given information into perimeter formula}
2x + 4x + 6 = 78   {used distributive property}
6x + 6 = 78   {combined like terms}
6x = 72   {subtracted 6 from each side}
x = 12   {divided each side by 6} 

width = 12 cm

- Algebra House