Explanation
Step 1
[tex]\begin{gathered} y=3x+12\Rightarrow y=mx+b \\ then,\text{ } \\ m=\text{ slope=3} \\ \end{gathered}[/tex]the slope we are looking for is the same because the lines are parallel
[tex]m_1=m_2[/tex]Step 2
Now, find the slope-intercept equation using P(4,5) and slope=3
[tex]\begin{gathered} y-y_0=m(x-x_0) \\ y-5=3(x-4) \\ y-5=3x-12 \\ y=3x-12+5 \\ y=3x-7 \end{gathered}[/tex]