Thinking Mathematically (6th Edition)

$9,466$
$D=500 \\C=100 \\L=50 \\X=10 \\V=5 \\I=1$ Note that: (1) When a smaller number is written before a bigger number, the smaller number is subtracted to the bigger number. (2) A bar on top means the value will be multiplied by $1000$. Thus, $\overline{IX}CDLXVI \\= (10-1)(1000) + (500-100) + 50+10+5+1 \\=9(1000)+400+66 \\=9000+466 \\=9466$