Answer: 54 cm^2
Explanation:
The area of a triangle is base*height/2.
To find the missing side of this triangle we can use pythagorean theroem. Let the unknown side = x
15^2 = 12^2+x^2
225 = 144+x^2
x^2 = 81
x = 9
Area = BH/2
Area = 9*12/2
Area = 54 cm^2