standard form: ax + by = c
slope intercept form: y = mx + b
For example, let ax + by + c equal 10x + 5y = 20
Isolate the y. Note the equal sign. What you do to one side, you do to the other.
Subtract 10x from both sides
10x (-10x) + 5y = (-10x) + 20
5y = -10x + 20
Next, to isolate the y, divide 5 from all terms
5y/5 = (-10x + 20)/5
y = -2x + 4
y = -2x + 4 is your slope intercept form.
hope this helps