Answer:
55.5 u^2
Explanation:
Split the quadrilateral into 2 triangles. There are two ways to do this, but I'm only doing one of them.
On the 5-11 triangle, use the two of the lengths and plug them into the triangle area formula. (L x W)/2 = A
5-11 triangle area: 27.5
Do the same for the 7-8 triangle. Plug it into the same formula.
7-8 triangle area: 28
Add the two areas. 27.5 + 28 = 55.5