This is a simultaneous system of equations, we would need both equations, to solve for the variables.
we have
2x - 3y = 6 - ---i
x +7y = 2------ii
Let's modify equation ii, x +7y = 2 means x = 2 - 7y
Anywhere we see x in equation i, lets put in 2 - 7y instead
2( 2 - 7y) - 3y = 6
4 - 14y - 3y = 6
4 - 17y = 6
-17y = 2
y = -2/17
Lets put this result in equation ii