Ok lets work through them.

Out of that we get a few things. Can(regular) = 72 cubic inches. Can(large) = Can(regular) * 2.

Or in algebra terms.

The regular can can equal x, the large can would then be 2x, if x is 72, find 2x.

72 * 2 = 144.

The large can is 144 cubic inches.

Your answer is correct.

Well, the big cylinder is 64 times the small cylinder. In other words let the small cylinder be x, and the large 64x. If 64x is 6cm, what does x equal?