we can simply get the area of the whole rectangle, that is, the rectangle including the triangle in it, and then get the area of the triangle and subtract it from that of the rectangle, what's leftover, is the part we did not subtract, namely the shaded region.
[tex]\stackrel{\textit{\Large Areas}}{\stackrel{rectangle}{(5)(11)}~~ - ~~\stackrel{triangle}{\cfrac{1}{2}(\stackrel{b}{5})(\stackrel{h}{3})}}\implies 55~~ - ~~\cfrac{15}{2}\implies \cfrac{95}{2}\implies 47.5[/tex]
