18 = 2 x 32 and 55 = 5 x 11 so yes it is.
55 and 72 are relatively prime because they have no prime factors in common.
No.
Two numbers are relatively prime if their greatest common divisor (GCD) is 1. The GCD of 55 and 121 can be determined by their prime factorizations: 55 is 5 × 11, and 121 is 11 × 11. Since they share a common factor of 11, their GCD is 11, meaning 55 and 121 are not relatively prime.
Yes
Any odd prime number.
No, they are not relatively prime.
55 and 72 are relatively prime because they have no prime factors in common.
No.
Yes, 55 and 62 are relatively prime because they have no common factor greater than 1.
Yes
Yes
No, they are not.
no
Yes, they are. 5 is the only prime factor of 25 and 5 is not a factor of 18, so they have no prime factors in common, which is what relatively prime means.
No.
Yes
Yes.