# How Are Linear Equations Used in Everyday Life?

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Linear equations use one or more variables where one variable is dependent on the other. Almost any situation where there is an unknown quantity can be represented by a linear equation, like figuring out income over time, calculating mileage rates, or predicting profit. Many people use linear equations every day, even if they do the calculations in their head without drawing a line graph.

## Variable Costs

Imagine that you are taking a taxi while on vacation. You know that the taxi service charges $9 to pick your family up from your hotel and another$0.15 per mile for the trip. Without knowing how many miles it will be to each destination, you can set up a linear equation that can be used to find the cost of any taxi trip you take on your trip. By using "x" to represent the number of miles to your destination and "y" to represent the cost of that taxi ride, the linear equation would be: y = 0.15x + 9.