Given Data:
The estimate amount of water used for drinking per day is: 172.%
The amount of water used by a given family for drinking is:68.8 gallons.
Let 'x' be the total gallons of water used by the family.
![\begin{gathered} x*(17.2)/(100)=68.8 \\ x=68.8*(100)/(17.2) \\ x=4*100 \\ x=400\text{ gallons} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/9dpojcadg3yrbelakk9tfebbjgm1wrojiu.png)
Thus, the family use 400 gallons of water per day.