Is y=-x^3+2x linear or non linear

What type of problem do you need with?

1) add 6 to 24, write the rest of the equation 10-2x= 30 subtract 10 from 30 2x=20 divide 20 by 2 and x=102) add 3 to -9 write the rest of the equation 4x+3=-6 subtract 3 from -6 4x=-9 x= -2.25  i don't know the rest sorry