Question 551960
You can think of the kite as 2 isosceles triangles,
a short one and a tall one, joined at their bases.
Let one of the long sides = {{{ x }}}
A short side will  be {{{ x - 6 }}}
Going around the perimeter,
{{{ 68 = x - 6 + x - 6 + x + x }}}
{{{ 68 = 4x - 12 }}}
{{{ 4x = 80 }}}
{{{ x = 20 }}}
{{{ x - 6 = 14 }}}
The sides are 14, 14, 20, and 20 cm
check:
{{{ 14 + 14 + 20 + 20 = 68 }}}
OK