Explanation:
Hey there!!
You can find the equation of a st.line passing through points using one point formula if only one point is given and slope is given , else find it by using two point formula (if 2 points are given).
Here, the points are, (4,8) and (-1,-12).
Using two point formula,

Keep all values,

Now, simplify them.

y - 8 = 5x -20
5x -y -20+8 = 0
Therefore, 5x - y -12 = 0 is the required equation.
Hope it helps...