Let x be the number of photos in the 1st group; the number of photos in the 2nd group will be 2nd group (33 - x).
The ratio of the 1st group to the 2nd is 4/7 OR:
x/(33-x) = 4/7 . (cross multiplication):
7x = 4(33 - x) → 7x = 132 - 4x
7x + 4x = 132 → 11x = 132 and x = 12
So if x = 12 , then the 2nd group = 33-12 = 21.
Proof: 12/21 (simplify by 3) = 4/7
