Given relation is
R=(a,b):gcd(a,b)=1,2a=b,a,b∈Z
Now,
Reflexive:
gcd(a,a)=1∀a∈Z, hence R is not reflexive.
Symmetric:
a=2,b=1⇒gcd(2,1)=1
Also, 2a=4=b
Now when a=1,b=2⇒gcd(1,2)=1
But, 2a=2=b
Hence, a=2b
⇒R is not Symmetric
Transitive:
Let a=14,b=19,c=21
gcd(a,b)=1
gcd(b,c)=1
gcd(a,c)=7
Hence, not transitive
So, R is neither symmetric nor transitive.