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# Write variable expressions to represent diagrams

Write an expression for the area of the rectangle.

 Area of a rectangle= = Length ·Width = (x+2)·x Substitute

Write an expression that represents the length of the red line.

The red line and the black line are the same length:

 length of red line = length of black line

The black line is the sum of its segments, so:

length of black line = m+ 2m= 3m

The length of the red line is 3m.