Elite marathon race times improved from 5 to ~20 years, remained linear between ~20 and ~35 years, and started to increase at the age of ~35 years in a curvilinear manner with increasing age in both women and men. The sex difference in elite marathon race time increased non-linearly and was lowest at the age of ~49 years.
D. Take the log of both sides first. You would then go on to solve by pulling the x down in front of the log 6 to get x log 6 = log 24. Divide both sides by log 6 to get x = log 24/log 6 and x = 1.7737
