8. (6 points) The three-digit number $2 a 3$ plus 326 equals $5 b 9$. If $5 b 9$ is a multiple of 9, then $a+b=$

 untranslated portion:
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(6 points) The three-digit number $2 a 3$ plus 326 equals $5 b 9$. If $5 b 9$ is a multiple of 9, then $a+b=$
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【Answer】Solution: Since $5 b 9$ is a multiple of 9, then $b=4$, because $549-326=223$, so $a=2$, therefore $a+b=2+4=6$. Hence the answer is: 6.