For example, suppose it costs "10 dollars per pound" to buy lobster.
The cost or the amount that you pay is a dependent variable because it depends on the number of pounds of lobster that you buy.
1. A recipe says to use 1/2 tablespoon of salt for every 2 pounds of ground meat.
The number of tablespoons of salt that you use is a dependent variable since the amount depends of how much ground meat you use.
2. A car can travel about 30 miles on one gallon of gas.
The number of miles you can travel is a dependent variable since the distance you can travel depends on how much gas you have in the vehicle.
3. Let R = 2X + 1 be the revenue that you generate for selling an item with X being the number of items you sell.
R or the revenue is a dependent variable since your revenue depends on the number of items you sell.