That's the i don't understand how you get -43a and -6

Distribute 8a by 5a and because there's two a's its a squared then distribute 8a by -6 which gives you -48a then you distribute the positive 1 by 5a which gives you 5a then distribute it the positive 1 by -6 and then combine like terms

hope it is correct if not i'm srry i tried to