To solve this problem you must apply the proccedure shown below:
1. You have the following expressions shown in the problem above:
(8m^2-6/n+3) + (9m^2-4/n+3)
2. As you can see, they have equal denominators, then you have:
(8m^2-6+ 9m^2-4)/(n+3)
3. Therefore, when you sum, you have the following result:
(17m²-10)/(n+3)
The answer is: (17m²-10)/(n+3)