8% less
100-8=92
P=present amount
F=future amount=f(t)
t=time in years
rate of decay is 8% or times 92%

is the equation or

is the equation or
It was about 17.4%
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% error=
actual value-estimated value
Then divide that by actual value
The expressions in which the numbers, or variables, or both, are connected by operational signs (+, - etc.) are called algebraic expressions. For example 5, 4x, a+b, x−y.
Can you put more information into this question