Math, please help me :o?

You're correct about question 1. The formula

V = Bh

only applies if the figure has the same cross-section area for any plane parallel to that of the base and intersecting the figure.

2a. The prism is 7cm by 10 cm by 12 cm, and since it's a right rectangular prism, 1-cm cubes will fit within it without waste space, so a total of

7 * 10 * 12 = 840 cubes will fit,

corresponding to its volume of 840 cubic cm.

2b. With 2-cm cubes, we have a problem with waste space because one of the dimensions is odd, so we cannot simply divide the volume (840 cubic cm) by the volume of a cube (8 cubic cm) and use that answer (105).

But we can fill a right rectangular prism 6 by 10 by 12 with 2-cm cubes, using

6 * 10 * 12 / 8 = 720/8 = 90 cubes,

and the remaining 1 by 10 by 12 space is the waste space because the cubes don't fit neatly.

2c. The prism has 6 rectangular faces, 2 with each possible combination of dimensions, so its surface area is

2 (7 * 10 + 7 * 12 + 10 * 12)

= 2 (70 + 84 + 120)

= 2 (274)

= 548 square cm.