Area and perimeter

The perimeter of a rectangular sandbox is 34 feet.If the length of the sandbox is 8 feet,what is the width of the sandbox

L = length 

W = width 

P = perimeter

$\begin{array}{rcll} P &=& 2\cdot L + 2\cdot W \\ 34 &=& 2\cdot 8 + 2\cdot W \\ 34 &=& 16 + 2\cdot W \qquad | \qquad - 16\\ 34-16 &=& 2\cdot W \\ 18 &=& 2\cdot W \qquad | \qquad :2\\ \frac{18}{2} &=& W \\ 9 &=& W \\ \end{array}$

The width of the sandbox is 9 feet.

Perimeter is the length around the whole box. If the lengths are 8 feet, you have 8 feet on two sides which is 16 feet. That means you have to subtract 16 from 34 and divide your answer by two since you need the other two sides. That will give you your width.