A3. How many pairs $(m, n)$ of natural numbers satisfy the condition $\frac{3}{m}+\frac{2}{n}=1$ ?
(A) 2
(B) 3
(C) 4
(D) 5
(E) More than 5.
A3. It is clear that $m>3$ and $n>2$. Since $\mathbf{z}$ with increasing $m$ the number $n$ decreases, we see that the only possible solutions are $(m, n) \in\{(4,8),(5,5),(6,4),(9,3)\}$.