Let \( t \) be the number of seconds after the filling begins.
For the first vat:
- Initial amount = 16 gallons
- Rate of filling = 12 gallons/second
The amount of liquid in the first vat after \( t \) seconds will be: \[ \text{Amount in first vat} = 16 + 12t \]
For the second vat:
- Initial amount = 23 gallons
- Rate of filling = 10 gallons/second
The amount of liquid in the second vat after \( t \) seconds will be: \[ \text{Amount in second vat} = 23 + 10t \]
We are looking for the time \( t \) when both vats have the same amount of liquid: \[ 16 + 12t = 23 + 10t \]
Now, let's solve for \( t \).
- Subtract \( 10t \) from both sides: \[ 16 + 2t = 23 \]
- Subtract 16 from both sides: \[ 2t = 23 - 16 \] \[ 2t = 7 \]
- Divide by 2: \[ t = \frac{7}{2} = 3.5 \]
Thus, the time \( t \) when both vats have the same amount of liquid is: \[ \boxed{3.5} \text{ seconds} \]