15. (3 points) There is a three-digit number $A$, after adding a decimal point before one of its digits, the resulting number is $B$. If $A-B=478.8$, then $A=$ . $\qquad$
【Solution】Given: $A-B=478.8$, then: $B$ is obtained by reducing $A$ by 10 times
$$
\begin{array}{l}
478.8 \div(10-1) \\
=478.8 \div 9 \\
=53.2
\end{array}
$$

So $A=53.2 \times 10=532$. Therefore, the answer is: 532.