Question

Where q represents the quanity

Answer 1

We have the following equation:
 Q = Qo * exp (-k * t)
 Substituting values we have:
 20 = 24 * exp (-0.00011 * t)
 We clear the value of t:
 exp (-0.00011 * t) = 20/24
 We apply Neperian logarithm to both sides:
  ln (exp (-0.00011 * t)) = ln (20/24)
 -0.00011 * t = ln (20/24)
 t = ln (20/24) / (- 0.00011)
 t = 1660 years
 Answer:
 t = 1660 years

Answer 2

Hello,
Please, see the attached file.
Thanks.