ANSWER
[tex]x = 3[/tex]
EXPLANATION
If the equation is parallel to the y-axis, then its slope is undefined.
The equation of a line that is parallel to the y-axis and passes through
[tex](x_1,y_1) [/tex]
is given by:
[tex]x = x_1[/tex]
The given line is parallel to the y-axis and passes through (3,7).
It's equation is
[tex]x = 3[/tex]
