To write an equation in slope-intercept form (y=mx+b) we need the slope (m) and the y-intercept. (b)
We are already given the slope as -5, so we know our equation will look like y=-5x+b.
Now we just need to find that y-intercept. (the value of y when x=0)
As a fraction, our slope -5 can be written as -5/1.
Rise-over-run-wise, this means that if y changes by 5, x changes inversely by 1.
(or vice versa)
We can take our point (3, 4)...
We want x to equal 0. (basically, subtracting 3 from x)
According to our slope, this would mean adding 15 to y.
Our y-intercept would be at (0, 19), with the value we put into our equation b=19.
y = -5x + 19