The woman is 61.5 inches tall.
This question is essentially asking for how many standard deviations the woman's height is away from the mean men's height.
Only 1 in 400 (or 0.25%) of men is shorter than our picky homegirl. If you think of a normal distribution of men's heights, this is the extreme left tail end. As a rule of thumb, +/- 3 standard deviations around the mean captures 99.5% of a population, leaving 0.5% outside of the interval (so, only 0.25% on each end). So we know that our girl refuses to marry anyone lower than -3 standard deviations from the mean.
All that's left is to plug in the given mean and SD:
69 -3(2.5) = 61.5 inches
