if it crosses the y-axis as -12, that means that's its y-intercept, and we know its slope.
[tex]\begin{array}{|c|ll} \cline{1-1} slope-intercept~form\\ \cline{1-1} \\ y=\underset{y-intercept}{\stackrel{slope\qquad }{\stackrel{\downarrow }{m}x+\underset{\uparrow }{b}}} \\\\ \cline{1-1} \end{array}~~ \implies ~~y=\stackrel{\stackrel{m}{\downarrow }}{5}x\underset{\underset{b}{\uparrow }}{-12}[/tex]
