Perimeter is basically the combines sum of all the bedroom's sides. It is a rectangle, therefore the formula is 2L+2W=P.
Since you are given the overall perimeter, you just plug-in the info you already have into the question. Like this: 2(11)+2(W)=46
Then solve the equation.
(2*11)+2W=46
22+2W=46
2W= 24
W=12 Feet. The width is 12 feet.
