Ax+By=C
Usually I find to points and put it in point slope form y-y1=m(x-x1)
For example
Let’s say the point is (2,3) and the slope (m) is 5 plug it in to get
Y-3= 5(x-2)
Then distribute
Y-3 = 5x -10
Then get all the regular numbers on one side and the variables on the other
-5x + y = -7
But the A can’t be negative so times everything by -1 to get
5x -y = 7