Once you know gallons per minute, set up an equation using $\text{rate} \times \text{time} = \text{amount}$ to find how many minutes are needed for 7 gallons.

Your equation will give the time in minutes. Remember there are 60 seconds in 1 minute; use this to convert your answer to seconds before choosing among the options.

In Desmos, type

This expression takes the fraction of the 4 minutes needed for 7 gallons and converts it to seconds. Look at the numeric value Desmos gives; that is the number of seconds the faucet needs to dispense 7 gallons. Match that value to the closest answer choice.

We are told the faucet dispenses 12 gallons in 4 minutes.

Compute the rate in gallons per minute:

So the faucet dispenses 3 gallons each minute.

Let $t$ be the time in minutes it takes to dispense 7 gallons.

We know:

• rate $=$ 3 gallons per minute
• amount $=$ 7 gallons

Use the relationship

So:

Solve the equation $3t = 7$ for $t$:

This is a little more than 2 minutes (since $7/3 \approx 2.33$).

There are 60 seconds in 1 minute, so multiply the time in minutes by 60:

Compute:

So it takes 140 seconds to dispense 7 gallons, which corresponds to answer choice C.