Explanation:
it says in the headline here : "college".
really ???
this is basic triangle calculation.
the yellow (shaded) area is the total area of the large triangle minus the area of the small (white) triangle.
both area right-angled triangles, so their areas are simple :
leg1 × leg2 / 2
the area of the full large yellow triangle is therefore
31.6 × 33.1 / 2 = 522.98 in²
the area of the small white triangle is
17.1 × 17.9 / 2 = 153.045 in²
that means the shaded area alone is
522.98 - 153.045 = 369.935 in² ≈ 369.94 in²