Ok so what your gonna do is add or subtract the ones with the same exponent.
so -15+4= -11 since they are both n^5 you can add them so your answer is:
-11n^2
now you have 8k^2-k-5k+7-2k. so you are gonna rearrange them so the same exponents are together.(keep the sign in front in front, if no sign it is positive)
