Distribute the negative into (2a-4b) so now ur equation is -2a+4b - 5(b+6a)
Then you are going to disibute your -5 and get -5b-6a
now your equation is -2a+4b-5b-6a
now u simply subtract -2a-6a which is -8a
then you subtract 4b-5b and get -1b or you could just say -b
now ur final answer is -8a-b