What you are looking for is the probability of of those 3 tickets being front row tickets. Probability is the maths of chance. A probability is a number that tells you how likely, or probable, something is to happen. This most commonly used example of probability is of rolling a die. Each number has a 1 in 6 chance of being rolled, making a probability of .16666 rec.
The Odds are Even for the Odd Numbers
We know that out of the 6 sides of the die, there are 3 odd numbers on a die (1, 3 and 5) and 3 even numbers (2, 4 and 6). The probability of rolling odd is the same as that of rolling even - 3 in 6 (or put more simply 1 in 2). 3 divide 6 is 0.5. There is a 0.5 probability of rolling an odd number, the same as for rolling an even number; or, expressed as a percentage, a 50% probability.
In your example, the probability of any of the 6 tickets being front row tickets is 4 in 6, or 0.6666 rec. or 66.7% (to one decimal place). As for the rest of the sum, here's a film to give you a few ideas: