answer is 27a^3+27a^2+9a+1 you should be able to do this but if not ill explain what i did first i used box(you can use foil technique if you want) and got 9a^2+6a+1(thats what i got from multiply 3a+1 against itself) then i took that answer and multiply it by 3a+1 because you wanted it cube not squared
