Final answer:
The value of f(6) is 19 gallons.
Step-by-step explanation:
The given equation represents the volume of water in a bathtub being filled per minute, where y represents the volume in gallons and x represents the number of minutes.
To find the value of y when x is 6, we substitute x = 6 in the equation y = 2.5x + 4:
y = 2.5(6) + 4
y = 15 + 4
y = 19
Therefore, f(6) = 19 gallons.