The line cross the Y axis in y=-2
The equation of a line is Y=ax+b where a is the slope and b the y intercept of the line
we know that for x=3 => y=4 then we plug the values we know in the equation of the line:
[tex]y=ax+b=2x+b[/tex]now we use the point we know:
[tex]4=2\cdot3+b[/tex]then solve for b
[tex]b=4-6=-2[/tex]The the y intercept of the line is y=-2