The perimeter of a rectangle (P) is found by adding the dimensions of the four sides of the rectangle. If we let W and L stand for the width and length, respectively, then
... P = W + L + W + L
Multiplication was invented to simplify repeated addition. Using multiplication, we can simplify this to
... P = 2W + 2L
The distributive property lets you simplify expressions where different things are multiplied by the same value. Using the distributive property, we can write the equation for perimeter as
... P = 2(W + L)
Using the given width and length, we can find the total length around the edge of the room to be ...
... P = 2(12.5 ft + 14 ft)
... P = 2(26.5 ft)
... P = 53 ft
53 linear feet of baseboards are needed to trim the room.