never
There are 2 sets of parallel lines.
4
I'm pretty sure it is 12 pairs of parallel lines.
It has 1 set of 3 parallel lines and 3 sets of 2 parallel lines, and 18 angles (3 sides meet at each vertex)
There are no parallel lines in a triangle !
never
there are 2 sets of parallel lines in a square
There are 2 sets of parallel lines.
A regular decagon would have five sets or parallel lines.
4
7
2
A square has four sets of parallel lines.
I'm pretty sure it is 12 pairs of parallel lines.
A square, a rectangle, a rhombus and a parallelogram are 4 sided quadrilaterals that have 2 sets of parallel lines.
well a rhombus has 2 sets of parallel lines