On your birthday you receive a pda for $300. the value of the pda decreases by 20% each year. Whatt will its value be 4 years from now? ... ?

This can function like a simple interest problem because there's a principal ($300), a rate (20% decrease or - 0.2 as a decimal each year), and a time (4 years).

I = Principal x rate x time = (300) (-0.2) (4) = - 240In 4 years, the PDA loses $240 worth of value. So it has a $60 value now (300 - 240).

NOW, that's assuming that the percent decrease is based on the $300 every year. If the percent decrease is based on the value each year, then it's different.