## Task 1 - 320611

$$
\begin{array}{cccc}
\mathrm{A} & \mathrm{A} & = & \mathrm{B} \\
\cdot & & - & - \\
\mathrm{C} & \mathrm{C} & = & \mathrm{D} \\
\hline \mathrm{E} & -\mathrm{F} & = & \mathrm{G}
\end{array}
$$

For the letters, basic digits $(0 ; 1 ; 2 ; \ldots ; 8 ; 9)$ are to be entered such that the same basic digits stand for the same letters and different basic digits stand for different letters, and that the given arithmetic operations are correctly solved.
The only natural numbers whose squares are different from the original number and are single-digit are Two and Three, so $A$ and $C$ are Two and Three, respectively.

$A=2$ and $C=3$ leads to a contradiction because of $A-C=F$, so it must be $A=3, C=2$, and thus $B=9$, $D=4, E=6, F=1$ and $G=5$, which is confirmed by the verification.