Hey Vincen,

Let's approach this problem by building equations. We'll let x equal the number of people in presently in line.

Statement 1

x + 2 ≥ 10
or simplified
x ≥ 8

So there might be 8 people in line. But there might also be 9, or 10, or 5000. We don't know. Insufficient.

Statement 2

x - 4 < 5
or simplified
x < 9

So there might be 8 people in line. But there might also be 7, or 6, or 0. Insufficient.

BOTH

8 ≤ x < 9
or
x = 8

So there must be 8 people in line, no more, no less. Both statements together are sufficient.

Let me know if I can provide more detail on how to build these equations based on the info in the question!