I really don't like to get questions like this but inevitably you will get at least one. Basically one approach to evaluating statements for theses types ofquestions is to do your best to create a case in which the question is answered with a YES and a case in which the question is answered with a NO. If using the data from a statement, you can create both cases, the statement is definitely insufficient. On the other hand, if whichever case you come up always answers the original question the same way (only YES or only NO), then the statement is sufficient.
Merging the statements works the same way. In this question, when evaluating both statements we could build the following cases:
Case 1: Top 4=16% each. 5th=7%. X=4.8%. Remaining 153 countries=tiny%
Case 2: Top 4=16% each. 5th=6.8%. 6th=5%, X=4.8% Remeaining 152=tiny%
In the first case the question "Is X in the top 4" would be answered with a YES. In the 2nd casee, the question would be answered with a NO. So we don't have sufficiency. The answer is
E
If this still doesn't make much sense, study the detailed solution and the video solution at
GMATPrep question 1491
-Patrick