#### Answer

a. x + x + x + 2x + 2x = 28
b. x = 4
c. 4 centimeters, 4 centimeters, 4 centimeters, 8 centimeters, 8 centimeters

#### Work Step by Step

a. The equation for the perimeter is written as the sum of all of its sides equals 28: x + x + x + 2x + 2x = 28
b. Solve by combining like terms and dividing to solve for x:
7x = 28
x = 28/7 = 4
c. If three sides have lengths of x and x = 4, then those sides are 4 centimeters. The sides with lengths of 2x are 2*4 = 8 centimeters.