If you have a problem with ratio, i would start with adding the numbers of the ratio, in our case:4+7=11
this means that the "whole" could be dividied into 11 parts, of which the first entity in the ratio has 4 and the other 7
since there are 33 photos, then each part is 33/11=3 photos.
so the two groups are 4*3=12
and
7*3=21
12 and 21 photos.
