The sum of three consecutive odd numbers is 51

Tried a whole bunch of odd sequences:

11 + 13 + 15 = 39

Nope too small.

21 + 23 + 25 = 69

Woah too big!

And after a few more trials found that:

17 + 19 + 21 = 51

Woohoo!

An odd number is ussualy written as "2k+1" and an even number is written as "2k".

Now, as there are 3 consecutive odd numbers that sum to 51, it can be written this way:

(2k+1) + (2k+3) + (2k+5) = 51

6k+9=51

6k=42

k=7 = > The numbers are: 2*7+1=15

2*7+3=17

2*7+5=19

15+17+19=51