Let the ionisation constant of the acid be Ka.
Degree of dissociation at 0.066M concentration =0.0145
Applying α=√KaC
0.0145=√Ka0.066...(i)
Let the degree of dissociation of the acid at 0.02M concentration be α1
α1=√Ka0.02...(ii)
Dividing eq (ii) by (i)
α10.0145=√0.0660.02=1.8166
or α1=0.0145×1.8166=0.0263