I think you'd answer it like this;
£105 / 3 = 35.
So now we know 35 is the number that was multiplied.
You add the ratios, 2+3+4, which is 9.
35 x 9 = £315.
Millie gets 70
Josh gets 105
and that leaves 140 for Liberty.
The total amount of money before it was divided is : £315.