How Difficult?

It seems to me that the advent of calculators many years ago and their widespread use in secondary schools has caused a steady erosion in basic math skills and the understanding of math in general.
Some of the high school students that I teach are often unable to comprehend basic math concepts related to fractions, decimals, and percentages.

So how difficult would it be for a random adult to perform the calculation 12/0.125 and come up with an answer in their head within 15 seconds?

Would it be more likely for someone to be able to do this, or to be able to achieve an undergrad Math or Physics degree assuming they work extremely hard and only need a bare minimum pass?