Answer:
n = 30
Explanation:
5n = Mean of three numbers
391 = 1st number
n = 2nd number
n - 1 = 3rd number
Therefore, to solve for x, we can write this equation:
(391 + n + n - 1)/3 = 5n
391 + 2n - 1 = 15n (Lowest Common Denominator is 3)
2n - 15n = -390 (Like terms)
-13n = -390
n = -390/-13
n = 30
Proof of n= 30 is correct:
(391 + n + n - 1)/3 = 5n
(391 + 30 + 29)/3 = 5 * 30
450/3 = 150
150 = 150
We proved n = 30 is correct