Let \( t \) be the time in minutes.
For the first vat, starting from empty and filling at 6 gallons per minute, the amount of liquid in the first vat after \( t \) minutes is: \[ 6t \text{ gallons} \]
For the second vat, which starts with 28 gallons and fills at 4 gallons per minute, the amount of liquid in the second vat after \( t \) minutes is: \[ 28 + 4t \text{ gallons} \]
We want to find the time \( t \) when the two vats have the same amount of liquid, so we set the two expressions equal to each other: \[ 6t = 28 + 4t \]
To solve for \( t \), we can first subtract \( 4t \) from both sides: \[ 6t - 4t = 28 \] \[ 2t = 28 \]
Now, divide both sides by 2: \[ t = 14 \]
Thus, the two vats will have the same amount of liquid after 14 minutes.