Answer :
x - length of the 3rd side
[tex]7+9>x \wedge 7+x>9 \wedge 9+x>7\\ x<16 \wedge x>2 \wedge x>-2\\ x\in(2,16)[/tex]
[tex]7+9>x \wedge 7+x>9 \wedge 9+x>7\\ x<16 \wedge x>2 \wedge x>-2\\ x\in(2,16)[/tex]