Answer:
A triangle ABC has 3 sides and they have to satisfy the following.
| a - b | < c < (a+b)
length of a side must be less the sum of the other two and more than the difference between the other two.
Hence, the third side, has to be more than (15-12) = 3 cm. Also it has to be less than (15+12) = 27 cm. It is in between 3 cm and 27 cm