The perimeter of a rectangle is equal to the sum of all sides of the rectangle.P=L+L+W+W=2L+2WP=L+L+W+W=2L+2WSubstitute the values of the length L=10xL=10x and width W=(4x−9)W=4x-9 into the formula for the perimeter of a rectangle.P=2⋅(10x)+2⋅(4x−9)P=2⋅10x+2⋅4x-9Simplify each term.
P=20x+(8x−18)P=20x+8x-18Simplify by adding terms.
P=28x−18
