Let \( t \) represent the time in minutes. We can set up equations for the amount of liquid in each vat over time.
For the first vat (starting empty and filling at 6 gallons per minute): \[ \text{Amount in vat 1 at time } t = 6t \]
For the second vat (starting with 28 gallons and filling at 4 gallons per minute): \[ \text{Amount in vat 2 at time } t = 28 + 4t \]
We want to find the time \( t \) when both vats have the same amount of liquid: \[ 6t = 28 + 4t \]
To solve for \( t \), we first subtract \( 4t \) from both sides: \[ 6t - 4t = 28 \] \[ 2t = 28 \]
Now, divide both sides by 2: \[ t = 14 \]
Therefore, the two vats will have the same amount of liquid after 14 minutes.