Answer :
just combine the x terms and the number terms exg
3x+4x=x(3+4)=7x
so 4x-5+(-7x)+9=
4x-5-7x+9
(4x-7x)+(-5+9)=
x(4-7)+(4)=
-3x+4
or 4-3x
3x+4x=x(3+4)=7x
so 4x-5+(-7x)+9=
4x-5-7x+9
(4x-7x)+(-5+9)=
x(4-7)+(4)=
-3x+4
or 4-3x