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put this solution on YOUR website!In a rectangle, there are two pairs of parallel lines.
If we labelled a length of one pair of lines as x and the other length pair of lines as y, the equation will look like this;
2x + 2y = 50
Subtitutes y = 20
2x + 2(20) = 50
2x + 40 = 50
2x = 50 - 40
2x = 10
x = 10/2
x = 5