共有多少隻狗?

$$\begin{array}{r}&5\\+\!\!\!\!\!\!&3\\\hline&8\end{array}$$

$$\begin{array}{r}&3\\-\!\!\!\!\!\!&5\\\hline&2\end{array}$$

$$\begin{array}{r}&5\\-\!\!\!\!\!\!&3\\\hline&8\end{array}$$

$$\begin{array}{r}&5\\+\!\!\!\!\!\!&3\\\hline&2\end{array}$$

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