tolong ya kakkk mau d kumpul
[tex] \frac{(5 \times 50) + (4 \times 60) + (3 \times 70) + (n \times 80) + (6 \times 90)}{5 + 4 + 3 + n + 6} = 70\\ \\ \frac{250 + 240 + 210 + 80n + 540}{18 + n} = 70 \\ \\ \frac{1240 + 80n}{18 + n} = 70 \\ \\ 1240 + 80n = 70(18 + n) \\ 1240 + 80n = 1260 + 70n \\ 80n - 70n = 1260 - 1240 \\ 10n = 20 \\ n = \frac{20}{10} \\ n = 2[/tex]
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