We can see that there is square that is divided into 4 parts. Each part is divided into two triangles. Hence the square is made up of 8 triangles, as labelled below
Now if observe Triangle number 2 and 7 can also form a triangle Similarly triangle numbers 2 and 3,3 and 6 and 6 and 7 can also form a triangle. Hence total number of triangles =8+4=12