Ratio 18:24 in lowest terms

First you would find the highest number that can evenly divide into both 18 and 24, that number happens to be 6, so 18 divided by 6 is 3 and 24 divided by 6 is 4, so 18:24 in lowest terms is 3:4.

Treat it as a fraction. Divide by 6, gives you 3:4.

3 is a prime number, if you bump into a prime you won't be able to divide any further.