Can you plz me on 2, 3, and 4. thx if you can

Okay on number 3 you would do LWH (length times width times height) which is 3ft x 5in x 6in. you would change the 3ft into 36in because you have to change the feet into inches and theres 36 in 3 feet (3x12) then you would take 36 and times it by 5 to get 180 and then go to the 6in and subtract 1 1/2 which is 1.5  because half is 5. that would give you 4.5 then you'd take the 180 and multiply it by 4.5 and get 810 and then multiply by .02 to get 16.2 which is $16.20.

36 x 5 x 6
180 x (?)        ->  6-1.5= 4.5 is ?
180 x 4.5
810 x .02
16.2
$16.20

Idk i am in 5th grade lol