Answer:
The mean is 20
Step-by-step explanation:
17+19+21+23=80
80 div 4 = 20
A right triangle has one angle that's 90° and a corner that looks like an L. Obtuse triangles have one angle that's greater than 90°. In acute triangles, all the angles are less than 90°.
Step-by-step explanation:
-12 is a Irrational number