Hello!
So we want slope intercept form which is;
y=mx+b
Using your given values we can just plug into our equation and solve.
-1=(-4/5)(12)+b
b=-1+48/5
b=43/5 so now we have our last value which is the y-intercept
Now we get our final answer of;
y=(-4/5)x+43/5
Hope this helped you out some. Any questions please just ask. Thank you