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Solution

Let $N\equiv 3\pmod{\operatorname{lcm}(5,6,7,8)}$. $\operatorname{lcm}(5,6,7,8)=840$. So $N=840k+3$. For divisibility by $9$: $840k+3\equiv 0\pmod{9} \Rightarrow 3k+3\equiv 0\pmod{9} \Rightarrow k\equiv 2\pmod{3}$. Smallest $k=2 \Rightarrow N=1680+3=1683$.