Rectangle a is 15cm long. rectangle b is 40cm long and its width is 8 less than rectangle a. the area of rectangle b is double rectangle a. what is the width of rectangle b?

The width is 24. 

You can get this by setting the rectangle A width to x and the rectangle B width to x - 24. Then set the area of A multiplied by 2 equal to the area of B. You can then solve for x. 

B. 16is the absolute value