If 2/3 of the guests were male, then 1/3 of the guests were female.
To find the number of female guests, we can take 1/3 of the total number of guests.
1/3 * 60 guests = 20 guests.
Therefore, there were 20 female guests who attended the party.
#### 20
The answer is: 20
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
If Princeton invited a total of 60 guests to his gender reveal party and 2/3 of them were male, what is the number of female guests who attended the party?

### Answer:
