The equivalent ratios are 3 to 5, 24 to 40, and 6 to 10.
Ratios are equivalent when they can be simplified down to the same ratio, for example 2 to 4 simplifies to 1 to 2 (by dividing by 2), and so does 3 to 6 (by dividing by 3), so these are equivalent. We can find answers by first simplifying the original ratio 12 to 20, which we can do by finding common factors and dividing by them:
12 to 20
÷ 2
6 to 10 (here we have found one answer)
÷ 2
3 to 5 (and here is another answer)
We then get 24 to 40 by multiplying the original ratio by 2, so:
12 to 20
× 2
24 to 40
I hope this helps! Let me know if you have any questions :)