Answer
$= -3x^{3} - 5y^{3}$
Work Step by Step
1. Rewrite the order of the expression in order to ease simplification:
$5x^{3} + 9y^{3} - 8x^{3} - 14y^{3}$
$= 5x^{3} - 8x^{3} + 9y^{3} - 14y^{3}$
2. Use the distributive property
$= x^{3}(5 - 8) + y^{3}(9 - 14)$
$= x^{3}(-3) + y^{3}(-5)$
$= -3x^{3} - 5y^{3}$
