You can use simple equations to solve real life problems because you may need to subtract an amount of money to see if you got the right amount of change, or you may need to know how much something is when it is on sale for 20% off.
Examples
I gave the clerk $20.50 and my total was $17.23. How much change should I get back.
20.50
- 17.23 My change should
----------- Be $3.27.
3.27
