Problem - 159
Solve in integers the equation $2(x+y)=xy+7$.
Solve $y$ with respect to $x$ leads to $$x=\frac{7-2y}{2-y}=2+\frac{3}{2-y}$$
This implies that $3$ is divisible by $(2-y)$ which means $y=-1, 5, 1, 3$. Accordingly
$$(x,y = (-1, 3), (5, 1), (1, 5), (3, -1)$$