I assume 5,18 is meant to read 5/18
To add fractions you must find a common denominator. In this case it is 18 as both 3 and 9 divide into 18.
So, convert them to their equivalents by multiplying both the top and the bottom by the same amount to get the denominator equal to 18.
1/9*2/2=2/18
2/3*6/6=12/18
5/18=5/18
2/18+12/18+5/18=19/18
So the sum is 19/18 or 1 1/18