Answer
$$ 13m^2 -5 $$
Work Step by Step
Like terms must (1) be raised to the same power and (2) consist of the same variable (i.e. x and y are not like terms). It is also important to note that numbers are all like terms with each other when not multiplied by anything. Thus, combining like terms, we obtain:
$$ = (10+3)m^2 +(3-3)n-8+3 \\ = 13m^2 -5 $$
