5n is the mean of three numbers 391, n and n-1, find n

n = 30

Step-by-step 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