Can you give any other example …

When we put gas in our car, there is a relationship between the number of gallons of fuel that we put in the tank and the amount of money we will have to pay. In other words, the more gas we put in, the more money we’ll pay. Also, the less money we pay, the less gas we’ll put in our car. This relationship depends on the price of a gallon of gas. The price is the proportionality ratio that exists between the quantity “gallons of gas” and the quantity “money it takes to fill up.”

Meanwhile, another car can fill up with a different amount of fuel than ours. The price per gallon stays the same, so the relationship between the gallons put in and the money paid is the same and therefore, filling each car’s tank with gas is proportional because they follow the same proportionality ratio.

Example: “If every gallon of gas costs $2 and I have $30 in my wallet, I’ll be able to put 15 gallons in the tank and if I wanted to put in 20 gallons, I’d have to pay $40”