Real-life examples of linear equations include distance and rate problems, pricing problems, calculating dimensions and mixing different percentages of solutions. One application of linear equations is illustrated in finding the time it takes for two cars moving toward each other at different speeds to reach the same point. Another example is estimating how much a shirt on sale for $20 and marked down by 35 percent cost before the sale.
Another example of a real-life linear equation is estimating the dimensions of a set of four shelves whose width needs to be five times its height, given that the wood available for use is 72 feet. Another example is to estimate how much a store pays the manufacturer for a calculator that is being sold for $80 and has been marked up by 16 percent.
Linear equations are used in the form of mixing problems, where different percentages are combined to get a new percentage. For instance, water can be mixed with a secondary liquid such as alcohol. A linear equation in this case estimates the amount of a 60 percent alcohol solution that must be mixed with 5 gallons of a 30 percent solution to result in a solution of 45 percent.