Answer
$ 9m^3+11m^2-2m+9$.
Work Step by Step
The given expression is
$\Rightarrow (14m^3+3m^2-2m+15)-(5m^3-8m^2+6)$
Use distributive property and clear the parentheses.
$\Rightarrow 14m^3+3m^2-2m+15-5m^3+8m^2-6$
Add like terms.
$\Rightarrow 9m^3+11m^2-2m+9$.