9. (12 points) Four people, A, B, C, and D, have a total of 251 stamps. It is known that A has 2 more stamps than twice the number of B's stamps, 6 more stamps than three times the number of C's stamps, and 16 fewer stamps than four times the number of D's stamps. Therefore, D has $\qquad$ stamps.
【Solution】Solution: 2乙 $+2=$ 甲;  
3丙 $+6=$ 甲;  
4丁 $-16=$ 甲;  
By making the coefficients of 乙, 丙, and 丁 the same in these three equations, we get:  
12乙 $+12=6$ 甲;  
12丙 $+24=4$ 甲;  
12丁 $-48=3$ 甲;  
From the above, we can derive: 12甲 +12乙 +12丙 +12丁 $=12$ 甲 +6甲 +3甲 - 12 - $24+48=251 \times 12$;  
That is, 25甲 $=251 \times 12-12=250 \times 12=3000$.  
$$
\begin{array}{l}
\text { 甲 }=3000 \div 25=120 \text { (pieces) } \\
\text { 丁 }=(120+16) \div 4=34 \text { (pieces) }
\end{array}
$$

Answer: 丁 has 34 stamps.  
Therefore, the answer is: 34.