A rectangle is 3 times as long as it is wide, and its perimeter is 80 centimeters. Find its dimensions

Say the width is W and the length is L

L=3W (and of course W=W)

Now you use the perimeter formula P=2L+2W

80=2 (3W) + 2W)

80=6W+2W

80=8W Divide both sides by 8

W=10

Now that you know the width, substitute it back into L=3W to find the length

L=3 (10)

L=30

The dimensions are length: 30 cm and width: 10 cm