Find the one which does not belong to that group ?
Answer: B
30 = 3⊃3; + 3, 10 = 2⊃3; + 2, 520 = 8⊃3; + 8 and 130 = 5⊃3; + 5.
30, 10, 130 and 520 can be expressed as n⊃3; + n but not 630.