Question #f1ddd

Feb 10, 2017

This means the sum of the numbers is $5 \left(x - 1\right)$

Explanation:

$\to 1 + 5 + x + 10 + 15 = 5 \left(x - 1\right)$

$\to 31 + x = 5 x - 5$

(add 5, subtract x on both sides)
$\to 31 + 5 + \cancel{x} - \cancel{x} = 5 x - x - \cancel{5} + \cancel{5}$

$\to 36 = 4 x \to x = 9$

Check :
$m e a n = \frac{1 + 5 + 9 + 10 + 15}{5} = \frac{40}{5} = 8 = 9 - 1$ Check!