Среднее набора

\(\displaystyle 7{\small ,}\ 9{\small ,}\ 13{\small ,}\ 14{\small ,}\ 14{\small ,}\ 17{\small ,}\ 18{\small ,}\ x{\small .}\)

равно \(\displaystyle 15{\small .}\) Найдите \(\displaystyle x{\small .}\)

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