We can divide the region into 2 parts : a rectangle and a triangle.
The rectangle's width is also the triangle's base.
S(rectangle) = ab = length x width = 13 x 10 = 130
S(triangle) = 1/2bh = 1/2 x base x height = 5 x 10 x 1/2 = 25
<=> Area of the shaded region = 130 + 25 = 155
