length(l)= 15 inches right. since its a rectangle two sides of it are 15 inches, making it 30 inches in total. So now solve for x in this equation.
[tex]30 + 2x = 54 \\ 54 - 30 = 2x \\ 24 = 2x \\ \frac{24}{2} = \frac{2x}{2} \\ 12 = x[/tex]
the x is the width of one of two width length(which are equivalent to each other)
