I think you would just add the sides together. On 2, what's 24+24+24 (or 24 times 3, for each side)? On 3, 5+8+2+2. It would be two 2's because the unknown side is right across from the 2, so it has to be 2 to make the shape equal on both sides. On 4, each side is the same, so it's 40*6. You get it? On 7 and 8, try drawing out the shapes with the measurements. It'll give you a visual example so you can see what the shape looks like.
