An unfair die is twice as likely to roll an even number than an odd number. what is the probability of it rolling an odd number?

The probability is always expressed as a part of the whole. So, it can be in terms of fraction or percentage. The numerator is the number of possible events while the denominator is the number of total events. Let x be the number of times you roll an odd number. So, the number of times you roll an even number would be 2x. The total rolls would then be x + 2x. Thus, the probability of rolling an odd number is

Probability = x/(2x + x) = x/3x = 1/3