I think it’s A. Hope it’s right. Sorry if it’s wrong.
x=10 because you add the variables to get 5x and you do 46-6 to get 40. Then you subtract 40 from 90 to get 50 and divide by 5 to get 10 as ur answer.
So if you want to add
we distribute
a(b+c)=ab+ac so
-2(m+n-4)=-2m-2n+8
5(-2m+2n)=-10m+10n
n(m+4n-5)=mn+4n^2-5n
so total we ahve
-2m-2n+8-10m+10n+mn+4n^2-5n
group like terms
4n^2+-2m-10m-2n+10n-5n+mn+8
add like temrs
4n^2-12m+3n+mn+8
