We are asked to find for an expression that represents the perimeter of a picture frame which has a shape of a rectangle. The dimensions given are length of size x cm and a width of size 9 cm.
The formula for the Perimeter of a rectangle is given by
P=2L+2W
where L is the length and W is the width of the rectangle.
Hence,
P=2(x)+2(9)
Simplifying this values would give us a result of,
P=2x+18
Therefore, 2x+18 is the expression that represent the perimeter of the picture frame.