785. Solve the equation in integers

$$
3 x y+y=7 x+3
$$
$\triangle$ Express $y$ in terms of $x$ from the equation:

$$
y=\frac{7 x+3}{3 x+1}
$$

To separate the integer part of the resulting fraction, multiply this equation by 3:

$$
3 y=\frac{21 x+9}{3 x+1}=\frac{(21 x+7)+2}{3 x+1}=7+\frac{2}{3 x+1}
$$

From this, $3 x+1$ can only take the values $-2, -1, 1$, and 2. We will consider all four cases.

Answer: $(0 ; 3),(-1 ; 2)$.