To write the ratio, 120:100 in simplest form we will divide each number by the GCF (Greatest common factor) which is 20. Then the answer will be the simplest form of 120:100. Lets do it:-
way #1
\(\frac{120/20}{100/20}= \frac{6}{5}\)
way #2
120 ÷ 20 = 6
100 ÷ 20 = 5
120:100 = 6:5
So, the ratio, 120:100 in simplest form is 6:5.
Hope I helped ya!! xD