OK, take a question like 'which is bigger, one fifth or one third or one half'. Some people just know the bigger number on the bottom of the fraction means that is smaller, for unit fractions. Other people have to visualise the fractions as a pizza and compare the slices. A few people have to take an actual value like 30 and work out the values of each of the fractions. They all solve the problem, but the 'way they know' is different.

A longer example is at

http://sohcahtoa.org.uk/pages/maths_algebra-revision-card-so...