75 units squared.
Explanation: First find the area of the section of the triangle with the right angle : (8 x 10)/2 = 40 units squared. Then the other section of the triangle: (7 x 10)/2 = 35 units squared. Add those two products together to get 75 units squared.
It’s been a while since I’ve done geometry so I’m not sure if I’m right, but you could give this answer a try :)