Final answer:
The probability of not selecting a pecan from a bag containing an equal number of pecans, walnuts, and almonds is 2/3, since there are 36 non-pecan nuts out of a total of 54 nuts.
Step-by-step explanation:
The question asks for the probability of not selecting a pecan from a bag that contains equal numbers of pecans, walnuts, and almonds. The total number of nuts in the bag is 18 pecans + 18 walnuts + 18 almonds = 54 nuts. Since there are 18 pecans, there are 54 - 18 = 36 other nuts.
To calculate the probability of not selecting a pecan, we divide the number of non-pecan nuts by the total number of nuts, which gives us 36/54 = 2/3. Therefore, the probability of not selecting a pecan is 2/3, which is answer choice C.