Points A, B, C lie on one straight line, and AB = 4 cm BC = 7 cm then AC can be equal.

consider two cases:
1) when the letters on a straight line are arranged in the order: A, B, C then the length of AC is the sum of the lengths AB and BC, i.e. 4 + 7 = 11cm
2) but it can also be located in this order: C, A, B then the length of the AC is the difference in the lengths of BC and AB, i.e. 7-4 = 3cm
There can be no other cases (and if it can, then I myself would be interested to know about them)
Answer: AC = 11 cm, AC = 3 cm