What are you people on about? It's not subjective. It's a geometric figure composed of 15 vertices and 30 line segments. A closed figure composed of three sets of collinear line segments forms a triangle. How many triangles can be so formed from this figure? That is an objective question, and has a definite answer.
Triangles are 2-dimensional imaginary constructs which don't exist in reality, like squares or octagons. You will never find a true triangle, only a crude representation of what we believe a triangle looks like based on a bunch of rules we observe but haven't definitively proven, man. As far as we know, everything's made of spheres, right? -But triangles are supposed to have definite two-dimensional points - but they can't, because spheres don't have points like "we're thinking of" -- and there's shit circling around the spheres and whatever, and -- okay, maybe I was being a little too narrow-minded, and there are some weird 2D units at the center of it all operating on some principle we're unaware of, but I mean - probably not, right?
ETA: And pictures are represented on most PC monitors and phones by "squares," right? Maybe your brain can piece together an estimate of how many triangles you think are there by looking at it, or you could use an unproven formula which deviates from what you're seeing, but in "reality," you're probably looking at a, what, icosagon? uhhh... chillisagon?