Final answer:
The probability of randomly selecting a seat numbered 104 in a theater row with 20 seats numbered 101 to 120 is 1/20.
Step-by-step explanation:
The probability of randomly selecting a seat numbered 104 in a theater row with 20 seats numbered 101 to 120 can be calculated by dividing the number of favorable outcomes by the total number of possible outcomes. In this case, there is only one seat numbered 104, so the number of favorable outcomes is 1. The total number of possible outcomes is 20. Therefore, the probability is 1/20.