You would add the area of the square with the area of the triangle.
Square: length x width
In your case, it would be 100in²
Triangle: length x height x 1/2 (or length x width divided by 2)
16-10 would be 6 (height) 10-6= 4 (length)
6 x 4 x .5 = 12in²
100in²+12in²=112in²
The area is 112in²