we just need to see everything that is not x as a number.
if I asked
[tex]5 = 7x - 7(2) - 9[/tex]
we would solve it by combining like terms first. but, if I tell you not to do that, we would add 9 and 7(2) to both side and end up with
[tex]5 + 7(2) + 9 = 7x[/tex]
we would then divide both sides by 7
[tex] \frac{5 + 7(2) + 9}{7} = x[/tex]
math is always math... it's just how we look at it. so, do the same steps!
[tex]y = 7x - 7z - 9[/tex]
add 9 and 7z to both side
[tex]y + 7z + 9 = 7x[/tex]
divide both sides by 7
[tex] \frac{y + 7z + 9}{7} = x[/tex]
