You subtracted the amount of water already in the container, when you should add that to the amount supplied by the hose. The total amount of water is $\displaystyle{10}+{25}={35}\usepackage{cmbright}\Huge\$ gallons after one minute, $\displaystyle{20}+{25}={45}\usepackage{cmbright}\Huge\$ gallons after two minutes, or $\displaystyle{30}+{25}={55}\usepackage{cmbright}\Huge\$ gallons after three minutes. You need to find an equation that matches these numbers.