Step-by-step explanation:
[tex]pythagorean \: theorem \\ {hypothenes}^{2} = { {x}^{2} + {y}^{2} } \\ {17}^{2} = {x}^{2} + {15}^{2} \\ 289 = {x}^{2} + 225 \\ {x}^{2} = 64 \\ x = 8cm[/tex]
