13. (10 points) There are two warehouses, A and B. Warehouse B originally had 1200 tons of inventory. When $\frac{7}{15}$ of the goods in Warehouse A and $\frac{1}{3}$ of the goods in Warehouse B are moved, and then 10% of the remaining goods in Warehouse A are moved to Warehouse B, the weights of the goods in Warehouses A and B are exactly equal. How many tons of inventory did Warehouse A originally have?
【Answer】Solution: $1200 \times\left(1-\frac{1}{3}\right)=800$ (tons);
$$
\begin{array}{l}
800 \div(1-10 \% \times 2)=1000 \text { (tons); } \\
1000 \div\left(1-\frac{7}{15}\right)=1875 \text { (tons); }
\end{array}
$$

Answer: Warehouse A originally had 1875 tons of inventory.