check the picture below.
notice, if we put the 90° angle at the bottom, one leg from it will be horizontally straight and the other will be vertically straight.
Area of a triangle: 1/2(base * height)
base = 12 cm, height = 9 cm
Plug 12 for b and 8 for h.
1/2(12 * 8) = 48
A = 48 cm²
