If x is a three-digit number in which the hundreds digit is 1 greater

Let's start by translating the question statement into simpler language.

x is a 3-digit number, so it's something like 593 or 712.

The hundreds digit is "1 greater than the tens digit and 2 greater than the units digit." What numbers is this referring to? It's numbers where the hundreds digit is the greatest, then the next digit is 1 smaller, and the last digit is 1 smaller than that. In other words, our numbers must have 3 digits that are all decreasing by 1. The only possibilities are:

987
876
765
654
543
432
321
210

Since there are only a handful of possibilities, I'll probably actually jot these all down on my own paper, so I can look at them as I work through the statements.

We know that x must be one of these numbers. The question asks: which one?

1) When x is multiplied by 3, the tens digit of the result is 2.

Interesting. It would be easy to find the tens digit if I was multiplying the number by 10, for example. However, I don't know an easy way to find the tens digit after multiplying a number by 3. I'm going to start calculating based on my list above, and see if there's a pattern. I'll start with the smaller numbers, since those should be easier to multiply by 3.

210 * 3 = 630 - doesn't fit the statement, since the tens digit is 3
321 * 3 = 963 - doesn't fit the statement, since the tens digit is 6
432 * 3 = 1,296 - doesn't fit the statement, since the tens digit is 9

At this point, I realized that I don't need to do the whole calculation. Since I only want to know the tens digit, I only need to look at the tens digit and the units digit of each possible value of x. (However, this is starting to look like a time-consuming problem, and I may guess at this point if I'm behind on time.)

543*3 -> 43*3 = 129. This fits the statement! x might equal 543.

654*3 -> 54*3 = 162

765*3 -> 65*3 = 195

876*3 -> 76*3 = 228 This fits the statement! x might equal 876

We'll stop here, since we have two different possible values for x. We now know that this statement is insufficient.

2) When x is multiplied by 4, the units digit of the result is 2.

This statement will be much easier to work with, since we only need to look at the units digits, not the units AND tens digits like with the previous statement. We're only looking for values that have a units digit of 2 when multiplied by 4.

210*4 -> 0*4 -> 0
321*4 -> 1*4 -> 4
432*4 -> 2*4 -> 8
543*4 -> 3*4 -> 12 This fits the statement! x could be 543.
654*4 -> 4*4 -> 16
765*4 -> 5*4 -> 20
876*4 -> 6*4 -> 24
987*4 -> 7*4 -> 28

The only value of x that fits this statement, as well as the info in the question stem, is x = 543. Therefore, this statement is sufficient. The correct answer is B.

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.