Question 388556
Pythagorean theorem - http://goo.gl/UCW3
{{{A^2+B^2=C^2}}}
A and B must be legs so...
{{{A^2+8^2=18^2}}}
{{{A^2+64=324}}}
Minus 64 on both sides
{{{A^2=260}}}
Sqrt both sides
{{{A=16.1245155}}}