The slope intercept form of a linear equation is of the kind y = mx + b.
The standard form of a linear equation is Ax + By = C.
So, to get from y = mx + b to Ax + By = C, you follow these steps:
y - mx = b
=> y + (-m)x = b
=> (-m)x + y = b
For example get the standard form from y = 3x + 5
=> (-3)x + y = 5
where =
A = -3
B = 1
C = 5