There are \(3\) small triangles. (Only contains 1 triangle/each)

There are \(2\) medium triangles. (Contains 2 small triangles/each)

There are \(1\) big triangle.  (Contains 3 triangles)

So there are: \(3+2+1=6\left(triangles\right)\) in this figure

6 hình

Number the traingles as shown

There are 6 triangles : 1 ; 2 ; 3 ; 12 ; 23 ; 123