Answer:
h = 10.018 ≈ 10 m
Explanation:
Because this triangle is right, there are two ways to get base*height (the area); the two legs, or the hypotenuse and the altitude it is connected to. And those areas will be equal.
Therefore, 12 m * 18.2 m = 21.8 m * h.
Multiply: 218.4 = 21.8h
Divide: h = 10.018 ≈ 10 m