a)
[tex]4^2+h^2=6^2\\16+h^2=36\\h^2=20\\\\5^2+h^2=x^2\\25+20=x^2\\45=x^2\\x=\sqrt{45}=\sqrt{9*5}=3\sqrt5[/tex]
[tex]b) \\\\a^2+5^2=(\sqrt{61})^2\\a^2+25=61\\a^2=36\\a=6\\\\b=6+y\\b^2+5^2=13^2\\b^2+25=169\\b^2=144\\b=12\\12=6+y\\y=6[/tex]
