Divide 33 photos into two groups so the ratio is 4: 7.
how do you properly write the answer?
4 7
4 7
4 7
4+4+4=12
7+7+7=21
12+21=33
is that the answer? or should it be 12/21? or 12: 21?

To do this task the best way is always add both "sides" of ratio and divide whole group by this sum.
sum=4+7=11
33:11=3
Now we know how much is 1 and we can multiply by 4 and by 7 to find the answer.
3*4=12 - first group
3*7=21 - second group

Your result is ok.