Check the picture below.
so the perimeter of the kite is x+x+y+y, namely 2x + 2y.
[tex]\bf \textit{using the pythagorean theorem} \\\\ c^2=a^2+b^2\implies c=\sqrt{a^2+b^2} \qquad \begin{cases} c=\stackrel{hypotenuse}{x}\\ a=\stackrel{adjacent}{8}\\ b=\stackrel{opposite}{15}\\ \end{cases} \\\\\\ x=\sqrt{8^2+15^2}\implies x=\sqrt{289}\implies \boxed{x=17} \\\\[-0.35em] ~\dotfill[/tex]
[tex]\bf \begin{cases} c=\stackrel{hypotenuse}{y}\\ a=\stackrel{adjacent}{8}\\ b=\stackrel{opposite}{4}\\ \end{cases}\implies y=\sqrt{8^2+4^2}\implies y=\sqrt{80}\implies \boxed{y\approx 8.94} \\\\[-0.35em] ~\dotfill\\\\ 2x+2y\implies 2(17)+2(8.94)\implies 51.88\implies \stackrel{\textit{rounded up more}}{51.9}[/tex]
