Assume the base of the triangle is on the bottom four points because a congruent triangle can be made by reflecting the base on the top four points. For a triangle with a base of length 1, there are 3 triangles. For a triangle with a base of length 2, there are 3 triangles. For length 3, there are 2. In total, the number of non-congruent triangles is 3+3+2=8.
but if you can rotate it of reflect it to be the same, it is counted twice.
Hmmmm.... ALL 12 of my triangles have the equal side lengths of 1.....and 4 have bases 0f 3 I guess there is only two that can be found?
The question says nothing about rotating/flipping being the same triangle..... I still think there is 16.....reflected / rotated / flipped makes it another triangle in the diagram ..... IMO