First, recognize the difference in variables. There are two variables being used: x and y.
Next, tell if there are different exponents for each variable. Since there is only one exponent form for each variable, you don't need to worry about that here.
Lastly, just add together the like variables:
[tex]x^{3}+4y^{3}-2x^{3}+2y^{3}\\(x^{3}-2x^{3})+(4y^{3}+2y^{3})\\\\-x^{3}+6y^{3}[/tex]
Thus, your answer is [tex] -x^{3}+6y^{3}[/tex].
