How many positive integers between 5 and 31
a. are divisible by 3? which integers are these?

The draw in the attached figure

Step-by-step explanation:

1) A right triangle  is a triangle that has one right interior angle

see the attached triangle ABC to better understand the problem

2) An acute triangle , is a triangle that has the three interior angles less than 90 degrees

see the attached triangle DEF to better understand the problem

3) An obtuse triangle , is a triangle that has one interior angle greater than 90 degrees

see the attached triangle XYZ to better understand the problem