Total paint = 8 gallons
Used up amount = 1/4th gallon
The amount left, is the difference between the two.
That would be 1/4th subtracted from 8.
Or,
[tex]8-\frac{1}{4}[/tex]Taking common denominator, we solve:
[tex]\begin{gathered} 8-\frac{1}{4} \\ =\frac{8(4)-1}{4} \\ =\frac{32-1}{4} \\ =\frac{31}{4} \\ =7\frac{3}{4}\text{ gallons} \end{gathered}[/tex]