Can someone answer the highlighted question!!! PLEASE

The equation in slope intercept form is:
[tex] y=-3x+9 [/tex]
A line parallel to this would have the same slope, which means our line that passes through the point (0,-4) has a slope of -3. We now have to plug in 0 as our x and -4 as our y in y=-3x+b so:
[tex] -4=0x+b \implies \\
-4=b [/tex]
Our equation is then y=-3x-b