What nine consecutive numbers when added together = 81

Question

Ive got a few different versions of this question and am unsure how to solve.

e.g What nine consecutive numbers when added together = 72

What 5 consecutive numbers when added together = 50

Answer 1

Let x be the first #.

2nd # = x + 1

3rd = x + 2

4th = x + 3

5th = x + 4

6th = x + 5

7th = x + 6

8th = x + 7

9th = x + 8

The sum of all these numbers = 81

x + x + 1 + x + 2 + x + 3 + x + 4 + x + 5 + x + 6 + x + 7 + x + 8 = 81

9x + 36 = 81

9x = 45

x = 45 / 9 = 5

First # is 5. The next consecutive numbers are 6, 7, 8, 9, 10, 11, 12 and 13.

Answer the remaining questions in a similar manner.