Question 18
Divide the six positive integers 2, 3, 7, 13, 18, and X into three groups so that the first group contains one number, the second group contains two numbers, and the third group contains three numbers, where X must belong in the third group. If the number in the first group is greater than the sum of the numbers in the second group, and that the sum of the numbers in the second group is greater than the sum of the numbers in the third group, then what is the maximum possible value of $X$?