Question 486604

the answer is {{{ 30}}}

The major problem with this is to avoid counting a triangle twice.

Each edge has a small triangle with no cross lines: {{{5}}}

Each vertex has a small triange with no cross lines: {{{5}}}

Each edge has {{{2}}} triangles with {{{1}}} cross line (its small triagle merged with one of the small triagles of its 2 vertices): {{{10}}}

Each vertex (using its 2 original edges) has a triangle with {{{2}}} cross lines: {{{5}}}

Each original edge to the opposite vertex has a triangle with {{{5}}} little cross lines: {{{5}}}

{{{Total = 30}}}