Jill has a poster hanging in her room whose width is 212 in. shorter than its length. the perimeter of the poster is 103 in. how many inches long and wide is the poster?

The poster is a rectangle. 
P = 2 L + 2 W
where L is the length and W is the width of a rectangle.
L = W + 2 1/2 = W + 2.5
103 = 2 ( W + 2.5 ) + 2 W
103 = 2 W + 5 + 2 W
103 = 4 W + 5
4 W = 103 - 5
4 W = 98
W = 98 : 4
W = 24.5 in
L = 24.5 + 2.5
L = 27 in

The poster is 27 inches long and 24.5 inches wide.