Question

500 = 12,375 * 0.7749^(n-1)

n = ?

Answer 1

Divide by 12375 and take the logarithm.
.. 500/12375 = 0.7749^(n -1)
.. log(4/99) = (n -1)*log(0.7749)
.. n = 1 +log(4/99)/log(0.7749)
.. n ≈ 13.583