You just do what it says, combine like terms so if there is more than one number squared just add up the numbers.
You also what to put them in order for the biggest number to the smallest so if there’s squared cubed and Normal number you want to put it in the exact order I gave you.
So first let’s combine.
-20a^2 + 40a^2 = 20a^2
5b + 35b + 2b = 42b
-15c
Therefore this is the answer.
20a^2 + 42b - 15c