If 17 is increased to 23, the increase is what percent of the original number? (this is known as the percent of change.)

23-17=6
The percentage of increase:
(6/17)*100=35.2942%

The value increase= 23-17
                              = 6
The percentage is for 100%
Thus, the increase divided by the original value, gives you the answer.
So, 6/23 x 100% is equal to 26.08%
If we round that answer up we get, 26.1

Hope this helps :))