It totally depends on the value of 'a', and if 'a' changes, then (6a-2) immediately changes too. Whatever 'a' is at the moment, (6a-2) is 2 less than 6 times 'a'.
X+4x=35-20. 5x=35-20. 5x=15. X=3
Um..same, whats your favorite
Click here: https://mathbitsnotebook.com/Algebra1/Polynomials/PObispecial.html
and follow the last example on the page.
Y=-13×-10+4
y=130+4
y=134
y=-13×10+4
y=-130+4
y=-126
10=-13x+4
6=-13x
0.46~x
-10=-13x+4
-14=-13x
1.08~x