$-2x^2y^2z^4$ + $\frac{1}{3}$$x^2y^2z^4$ - $\frac{2}{5}$$x^2y^2z^4$
= ( -2+ $\frac{1}{3}$ - $\frac{2}{5}$ ).$x^2y^2z^4$
= ( -2 + $\frac{1}{3}$ - $\frac{2}{5}$) .$x^2y^2z^4$
= ( $\frac{-30}{15}$ + $\frac{5}{15}$ - $\frac{6}{15}$ ).$x^2y^2z^4$
= $\frac{-31}{15}$$x^2y^2z^4$