Remember that in order for three sides a, b and c to form a triangle, the following need to be true:
[tex]\begin{gathered} a+b>c \\ a+c>b \\ b+c>a \end{gathered}[/tex]Let's see what happens if:
[tex]\begin{gathered} a=5\operatorname{cm} \\ b=6\operatorname{cm} \\ c=10\operatorname{cm} \end{gathered}[/tex]This way,
[tex]\begin{gathered} a+b>c\rightarrow5\operatorname{cm}+6\operatorname{cm}>10\operatorname{cm}\rightarrow11\operatorname{cm}>10\operatorname{cm}\text{ }✅ \\ a+c>b\rightarrow5\operatorname{cm}+10\operatorname{cm}>6\operatorname{cm}\rightarrow15\operatorname{cm}>6\operatorname{cm}✅ \\ b+c>a\rightarrow6\operatorname{cm}+10\operatorname{cm}>5\operatorname{cm}\rightarrow16\operatorname{cm}>5\operatorname{cm}\text{ }✅ \end{gathered}[/tex]