First you need to find the area of the large rectangle then subtract the area of the smaller triangle.
area of the large triangle: (x + 10)(2x + 5), FOIL, 2x^2 + 5x + 20x + 50 =
2x^2 + 25x + 50.
area of the small rectangle: (x + 1)(x + 1), FOIL, x^2 + x + x + 1 =
x^2 + 2x + 1
Shaded region: 2x^2 + 25x + 50 -(x^2 + 2x + 1) =
x^2 + 23x + 49