ta có :
8 =\(\frac{7.5+8.3+9.n+10.1}{5+3+n+1}\)
8 = \(\frac{69+9.n}{9+n}\)
suy ra 8(9+n)=69 +9n
---> 72+8n=69+9n
---> n=3
Ta có
7*5+8*3+9*n+10*1/5+3+n+1=8
69+9n/9+n=8
>69+9n=8*(9+n)
>69+9n=72+8n
>n=80-78
N=2
Lộn
9n-8n=80-78
1n=2
N=2
k cho mình nha
Theo đề bài ta có : X = \(\frac{7\cdot5+8\cdot3+9\cdot n+10\cdot1}{5+3+n+1}=8,0\)
=> \(\frac{35+24+9n+10}{9+n}=8\)
=> \(69+9n=\left(9+n\right)\cdot8\)
=> \(69+9n=72+8n\)
=> \(9n-8n=72-69\)
=> \(n=3\)