Given the rectangles perimeter, find the unknown side lengths.

The perimeter is just adding all the sides together.

a.) 180 = 40 + 40 + x + x

180 = 80 + 2x Subtract 80 on both sides

100 = 2x Take 1/2 of 100 to get x

x= 50cm

b.) 1000 = 150 + 150 + x + x

1000 = 300 + 2x Subtract 300 on both sides

700 = 2x Take 1/2 of 700 to get x

x = 350

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