how should i solve this system of linear equation by substitution by first isolating x?

x + y = 9      →       x  =  9 - y      (1)       note......this isolates x

-10x + 6y = 6     (2)

Sub (1)  into (2)

-10 ( 9 - y) + 6y  = 6     simplify

-90 + 10y + 6y  = 6

-90 + 16y  = 6      add 90 to both sides

16y = 96     divide both sides by  16

y  = 6          and using (1),    x =  9 - 6   =   3