**Perimeter** is the distance around an object.

Perimeter of RectanglePerimeter = length + width + length + width

OR

Perimeter = 2 × length + 2 × width

Use the given information to set up an equation and solve for the width.

For the equation, use the sum of the sides, or use two times length plus two times width.

Perimeter | = | length | + | length | + | width | + | width |

60 feet | = | 20 feet | + | 20 feet | + | width | + | width |

60 feet | = |
40 feet | + | width | + | width |

60 feet | = |
40 feet | + | 10 feet | + | 10 feet |

**OR**

Perimeter | = | (2 × length) | + | (2 × width) |

60 feet | = | (2 × 20 feet) | + | (2 × width) |

60 feet | = | 40 feet | + | (2 × width) |

60 feet | = | 40 feet | + | 20 feet |

60 feet | = | 40 feet | + | (2 × 10 feet) |

The width of the rectangle is 10 feet.

First, find the sum of the side lengths that are given.

5 feet + 10 feet + 5 feet = 20 feet

Then, subtract the sum from the perimeter.

24 feet - 20 feet = 4 feet

The length of the missing side is 4 feet.