yes, they are.
No.
18/3 = 6/1
2x9=18
It is 7/6.
They are: 3 to 4
No, they have different ratios.
3 to 4
The ratio for 18/16 would be 9:8.
No. 4/7 and 16/28 and 28/49 are equivalent ratios. The 4 and the 7 must be multiplied by the same number in order to maintain the ratio.
Yes
504 = 18 x 28 = 28 x 18 252 = 9 x 28 = 14 x 18