Where is a place were you can use an equation in real life?

Answer 1

In business is one. A break-even analysis uses equations to help determine what sales volume is necessary to 'break even'. Break even is the point where the revenues are just enough to pay all of the bills (rent, utilities, payroll, products for resale, etc.). After you hit the break-even point, any sales over that, and after the cost of products needed to sell is paid, will be profits.

You could use a similar analysis to figure what grade you need to make on a test to push your average up to the next higher letter-grade.