What is 5 4/9 + 2 15/36 as a whole or mixed number? ?

You have to add the whole numbers, which is 5 + 2 = 7.  Then you add the fractions.  In order to do that, you have to convert 4/9 to X/36 so 15/36 and 4/9 have the same denominator.  In this case, 9 is a factor of 36, so you can multiply 4/9 by 4/4 (which is like multiplying by one).  The result is 16/36.  Now add the numerators 15 + 16 = 31.  Denominator remains 36 because you do not change it when you add fractions.

The result therefore is 7 and 31/36.