Answer:
1) Forms a proportion.
2)Does NOT form a proportion.
3)Forms a proportion.
4)Does NOT for a proportion.
5) X and Y are proportional.
Explanation:
1) If you simplified 5/10 it would equal 1/2, therefore this ratio is proportional.
2) There is no way to go from 4/6 to 18/24 that would allow it to be proportional.
3) Looking at the numerators you would multiply by 2 to go from 5 to 10. Looking at the denominators you would also multiply by 2 but to get from 3 to 6. Given the fact that they are both multiplied by two to get from one to the other, it is therefore proportional.
4) There is no way to go from 25/20 to 15/12 that would allow it to be proportional.
5) Y multiplies at a constant rate. From 1 birdhouse to 2 birdhouses you would multiply 2x12. From 2 birdhouses to 4, you would multiply 12x4 and so on.