To get the area of the shaded region, we must subtract the area of the bigger triangle on the outside and the area of the smaller triangle inside the bigger triangle.
Set up the equation:
Area of big triangle - Area of small triangle = [tex]\frac{1}{2} *19*19 - \frac{1}{2} *13*13[/tex][tex]= \frac{1}{2} (19^{2} -13^{2} ) = \frac{1}{2}*192 = 96[/tex]
