The answer would be 2160 because v=l*w*h so 10*12*18 would equal 2160
By moving the signs he actually changed the number itself. He changed -6 from a negative to a positive and 5 from a positive to a negative. Both equations give different answers.
Hopefully this helps :)
C. It is always a rational number. You cannot determine its sign without knowing the values of a and b.
He doesn't know where x is