Since [tex]y[/tex] is representing the number of gallons of water in the tub, we need to replace [tex]y[/tex] with the number of gallons remaining in the tube to find the time. Fortunately, the problem is telling us just that: 17.8 gallons. The only thing left is replacing that value in the equation, and solve for [tex]x[/tex] to find the time:
[tex]17.8=-7.3x+39.7[/tex]
[tex]7.3x=21.9[/tex]
[tex]x= \frac{21.9}{7.3} [/tex]
[tex]x=3[/tex]
We can conclude that after 3 minutes the tub will have 17.8 gallons of water remaining.
