Are those the only choice of flavors, Azzure? If so, then the total amount is 8 + 3 + 4 + 6 = 21. This means there are a total of 21 possible outcomes. Probability is equal to the target outcome divided by the total possible outcomes.
The probability of selecting grape is 6/21 = 2/7
The probability of selecting lemon is 3/21 = 1/7
