12. (4 points) In a division without a remainder, the sum of the dividend, divisor, and quotient is 103, and the quotient is 3. The dividend is ( )
A. 25
B. 50
C. 75
【Solution】Solution: Since the sum of the dividend, divisor, and quotient is 103, and the quotient is 3, the dividend + divisor $=103-3=100$;
Since the divisor $=\frac{\text { dividend }}{3}$,
the dividend is:
$$
\begin{array}{l}
100 \div\left(1+\frac{1}{3}\right) \\
=100 \div \frac{4}{3} \\
=75
\end{array}
$$

Therefore, the correct choice is: $C$.