The correct answer is:
12:21.
Step-by-step explanation:
Let x be the part of our 33 photos that represents 4 in our ratio. Then the second part of the ratio, the part that represents 7, will be 33-x, the remaining number of photos.
This gives us the ratio

Since we know we want this ratio to equal 4:7, we can set up a proportion:

To solve this, we cross-multiply:
x(7) = (33-x)(4)
7x = (33-x)(4)
We use the distributive property on the right:
7x = 33*4-x*4
7x = 132-4x
Add 4x to each side:
7x+4x = 132-4x+4x
11x = 132
Divide both sies by 11:
11x/11 = 132/11
x = 12
The smaller portion of photos, that represents the 4 in our ratio, is 12. This leaves 33-x=33-12=21 for the larger portion of photos. This gives us the ratio 12:21.