First you evaluate your parenthesis, and to do that you need to find the Least Common Denominator of 2/3 and 2/9. The least common denominator would be 9. 3 x 3 = 9 so you multiply 2 x 3 = 6. 6/9 - 2/9 = 4/9. 7/3 x 4/9
There are 6 different variants available for each croissant. There are 26 croissants in all out of which 1 is plain. We use combination and permutation technique to identify different ways to choose croissant.