You do it like this; you add the numbers of the ratio, 3 and 4, that is 7.
That means that you need to divide the original number into 7: 28/7=4.
This means that one "entity" is equivalent to 4.
Now we need to multiply the ratio by the "entity: 3*4=12 and 4*4=16. So the division is 12:16
