Ta có: \(\dfrac{6.3+7.5+8.23+9n+10.2}{3+5+23+n+2}=8\)
\(\Leftrightarrow8.\left(3+5+23+n+2\right)=6.3+7.5+8.23+9n+10.2\)
\(\Leftrightarrow8.\left(33+n\right)=18+35+184+9n+20\)
\(\Leftrightarrow8.\left(33+n\right)=257+9n\)
\(\Leftrightarrow8.33+8n=257+9n\)
\(\Leftrightarrow264+8n=257+9n\)
\(\Leftrightarrow9n-8n=264-257\)
\(\Rightarrow n=7\)
Vậy n = 7.
N=8.5=40
=>n=40-3-5-23-2=7
vậy n=7