yes
Yes
Yes
Because there are 540 interior degrees in a five sided figure and the total sum of three triangles is 540 degrees
Yes because there are 540 degrees in a pentagon and 180 degrees in a triangle so 540/180 = 3 triangles.
Absolutely. Any two congruent right triangles will form a rectangle, and if the right triangles are isosceles right triangles, they will form a square.
Yes. You can always draw a "diagonal" line between opposite corners of any four-sided figure. Then, cutting along that line, you wind up with two triangles out of which the figure could have been made.
You can always find opposite corners that can be connected with a line which divides the quadrilateral into two trilaterals.
A 16 sided polygon is made from 14 triangles
A dodecagon is a 12 sided shape made from 10 triangles
Rohmbus is a four sided figure (quadrilateral) that is made up of two equilateral triangles
Because all other polygons are made from triangles as for example an 8 sided octagon has 6 triangles within it or a 6 sided hexagon has 4 triangles within it.