1.)so for #1 your by is 8×3 and that goes in that box and you get 24 and so the 3 on top which is called cubed means you have to multiply 24 three times but you dont have to do that so your answer is 24ft^3
2.)ur base is 15 and your height is 3 so multiply these together and it equals 45meters^3
3.)the triangular prism volume is 6×4 which equals 24ft^3. the rectangular prism volume you multiply 4×6×12 and you get 288ft^3.at last for the composite figure you just add the volumes from the rectangular prism with the triangular prism and your answer would be 312ft^3.
4.) so this should now be easy because everything you did for example 3 is the the thing you do for example 4 it's not the same answer bit the same way to solve your answer.
p.s. sorry for the really long explanation