21. What is one possible length of the third side?

$$\begin{array}{lcl} The\:lengths\:of\:two\:sides\:of\:an\:isosceles\:triangle\:\\ are\:5\:and\:7.\:What\:is\:one\:possible\: length\:of\:the\:\\third\:side\:?\\ \end{array}$$