If f represents the amount of gas in the tank (in gallons), and there are fewer than 5 gallons of gas in the tank, then we can write this as an inequality:
f < 5
This inequality reads as "f is less than 5". It means that the value of f can be any number less than 5, but it cannot be equal to 5 or greater than 5.
For example, if there are 2 gallons of gas in the tank, then f = 2, which satisfies the inequality f < 5. But if there are 5 gallons of gas in the tank, then f = 5, which does not satisfy the inequality f < 5.