Here, I’ve answered this question before:
Standard form is Ax + By = C where A and B are coefficients to x and y respectively
So we have to move y to the right side and 3 to the left side, because 3 is the constant in this case, and therefore the C of our equation.
Since the sign changes after moving them over the equation, y and 3 will both be negative
-3 = 1x - y