Sorry for my english, i hope you understand.
If you want to check the proportion is true you just have to reduce each fraction
12/1 = 33/3 = 60/5
(33/3)/(3/3)= 12/1
60/5= (60/5)/(5/5)= 12/1
So you have 12/1 = 12/1 = 12/2, that's how you prove the proportion is true.
Now we want to write the ecuation, we know the proportion is 12/1. 12 is the amount of estudents and 1 is the amount of adults If you want to calculte the amout of adults you just hace to divide the amount of estudents in twelve
A (Adults)= Estudents / 12
E (Estudents) = Adults * 12
