a)
[tex] {x}^{2} + {4}^{2} = {5}^{2} \\ \\ {x}^{2} + 16 = 25 \\ \\ {x}^{2} = 9 \\ \\ x = \sqrt{9} \\ \\ x = 3[/tex]
b)
[tex] {y}^{2} + {15}^{2} = {17}^{2} \\ \\ {y}^{2} + 225 = 289 \\ \\ {y}^{2} = 64 \\ \\ y = \sqrt{64} \\ \\ y = 8[/tex]
