There are a total of 18 triangles:

9

3 small triangles ABC ACD ADE

3 medium triangles AFG AGH AHI

3 large triangles AJK AKL ALM

also 6 more

triangles

ABD ACE

AFH AGI

AJL AKM

3 more:

ABE AFI AJM

9

3 small triangles ABC ACD ADE

3 medium triangles AFG AGH AHI

3 large triangles AJK AKL ALM

also 6 more

triangles

ABD ACE

AFH AGI

AJL AKM

3 more:

ABE AFI AJM