Verified Answer :

so when dividing by a ratio you add the ratio
so 1+2+3= 6
so 42/6= 7
71=7
7
2=14
7*3=21
so the ratio is
7:14:21

Neuron

If you would like
to 
divide 42 in the ratio of 1 : 2 : 3, you can do this using the following
two steps:

First, add the numbers: 1 + 2 + 3 = 6
Second, divide and multiply: 1 / 6 42 = 7
                                             2 / 6
42 = 14
                                             3 / 6 * 42 = 21

The result you are looking for is 7 : 14 : 21.