Please help! Can someone explain to me this kind of math?
I've been having trouble understanding this.

It has to do with volumes of cylinders and the pythagorean theorem.

I'll use the first one to explain.

A cylinder has two main parts: the base (the shape at both ends, in this case a circle), and the height (the distance between the ends).

For these exercises, the "radius" and "diameter" refer to the radius and diameter of the base, which is 6 in and 12 in respectfully. The "B" means the area of the base, which is pi(6)² = 36pi. The "h" is the height, which is 18.

Now for the volume. If you remember, the volume of a box is the area of the base square multiplied by the height. It's the exact same thing here. The volume of a cylinder is the area of the base (B) times the height (h), which is

B * h = (36pi) * (18) = 648pi ≈ 2035.752 in³.

Try to do the other ones the same way, and let me know if you're stuck.

it would be:

c.parallelogram.