Answer:
![2t {}^(2) - 5t - 3](https://img.qammunity.org/2020/formulas/mathematics/middle-school/jbdmnrjvttyi3wor2yfmohldj6omeg67h9.png)
Explanation:
You add the like-terms so the things that are the same, pretty much.
so 3t^2+7t^2 = 10t^2
and you can subtract 8t^2 from 10t^2 because they are like terms so you get 2t^2
then bring -5t down and subtract 9 from 6 and boom you're done