Question 160786
I assume by % years you meant 5 years, so that in 5 years it depreciates to $0.
At time zero, the value is $37000.
At time 5 years (or 60 months), the value is $0.
What is the time, T, to reach a value of $8000.
Use straight line (linear) depreciation. 
Set up a ratio. 
{{{(37000-8000)/(0-T)=(37000-0)/(0-60)}}}
{{{(23000)/(-T)=(37000)/(-60)}}}
{{{T=(29*60)/37}}}
{{{T=47.02}}}
The computer is 47 months old.