Question

The price of coffee rose by 20% and is now $5.40 per jar. How do you find the cost of the same jar before the rise of the price?

Answer 1

Call the price before the rise: `P`; so now you have that:
`0.2P+P=$5.40`
and `P=$4.50`

The old price, `$4.50` was increased adding `0.2*$4.50=$0.90`