Question

You bought a guitar 6 years ago for $400. It's value decreases by about 13% per year. Write a formula to show the value of the guitar over those six years and determine its current value

Answer 1

This would be a depreciation formula
 which is value = Original price x (1-percent change)^time
 using the information from the problem 

Value = 400 x(1-0.13)^6

value = 400 x 0.87^6

value = $173.45