4
A full rotation = 360°; a right angle = 90° → there are 360° ÷ 90° = 4 right angles in a full turn.
An octagon may have 1, 2, 4 or 8 angles of rotation.
Four (where each right angle is 90 degrees and a complete turn is 360 degrees.)
12
4 right angles, no other angles.
A Pentadecagon had 15 sides
According to my calculations, I am a complete nerd, and the answer to your question is 0, there are no 90 degree angles in an octagonal prism.
It has 6 angles, none of which are right angles.
0 right angles
A regular hexagon as no right angles. An irregular hexagon could have from none to as many as five right angles.
there are 4 right angles as 1 right angle is 90 degrees and 90 x 4 = 360