Acertain computer loses half of its value every 2 years .how many years would the computer be worth 12.5 of its intial value

12.5% is equal to .125.

Using the formula:

A = P(1/2)^(t/h)

Where A is the amount, P is the original, t is the time in years, and h is the half-life. 

.125P = (1/2)^(t/2)

.125 = (√2)^t

ln(.125) = ln(√2) * t
t = ln(.125) / ln(√2)
t = 6 years