The answer is 12 m.
How to solve:
First find out the height of the bottom square, which is done by doing 3 x 3 which gives you 9
Next find out the height of the triangle by doing 5 - 3 which gives you 2
Find out the area of the triangle by doing 2 x 3 which gives you 6. 6 is not the area of one triangle but of two of them as a square. You need to divide 6 by 2 in order to find out the area of the triangle. This gives you 3.
3 + 9 = 12