The best way to solve this question is to use equation rather than getting stuck in remainder part

1) x = 100a+30 , where a is non-negative integer.

Thus x can take following values 30,130,230,330....etc

So the ten's digit always will be 3

Sufficient

2) x = 110a+30 , where a is non-negative integer.

Thus x can take following values 30,140,250,380....etc

So the ten's digit in not unique

In-Sufficient

Answer A

_________________

If you like my Question/Explanation or the contribution, Kindly appreciate by pressing KUDOS.

Kudos always maximizes GMATCLUB worth -Game Theory

If you have any question regarding my post, kindly pm me or else I won't be able to reply