Simply these expressions:

Question

8n^2 - 6n + 7n^2 - 4n +5
and
6x^2y + 5y - x^2 + 3y - 6y

Answer 1

8n^2 - 6n + 7n^2 - 4n +5
8n^2+7n^2 -6n-4n + 5
15n^2 - 10n + 5

do the 2nd one the same way. Collect all the terms with the same powers, then add up the coefficients.