[tex]\begin{gathered} \text{Firstly they drank }\Rightarrow50\text{ gallon of water} \\ \text{Then again half of it}\Rightarrow\frac{50}{2}=25gallon\text{ of water} \\ So\text{, they drank} \\ \text{Drank}=50+25 \\ \text{Drank}=75\text{ gallon of water(Ans)} \end{gathered}[/tex]
