the possible side lengths would be
4cm, 8cm, and 10cm
the rule is that, if you add any 2 numbers, the sum should be larger than the number you didn't add
these three numbers are the only ones that fit this
4 + 8 = 12 (larger than 10)
10 + 8 = 18 (larger than 4)
4 + 10 = 14 (larger than 8)
hope this helped!