The equation of any straight line can be written as in slope intercept form as -
[tex]\green{ \underline { \boxed{ \sf{y=mx+c}}}} [/tex]
where,
[tex]\begin{gathered}\begin{gathered}\\\implies\quad \sf y= 3x-9 \\\end{gathered} \end{gathered} [/tex]
[tex]\longrightarrow[/tex]Comparing the equation y = 3x -9 with the standard form of the equation, we get -
[tex]\quad \bull\: \sf m= 3[/tex]
[tex]\quad \bull \: \sf c= -9[/tex]
Thus, the line cross the y-axis at (0,-9) .