Question 638924
If {{{ x }}} is the width of the border, 
the border adds {{{ 2x }}}
to the length and width, so
{{{ ( 10+ 2x )*( 8 + 2x ) = 168 }}}
{{{ 80 + 16x + 20x + 4x^2 = 168 }}}
{{{ 4x^2 + 36x - 88 = 0 }}}
{{{ x^2 + 9x - 22 = 0 }}}
{{{ ( x + 11 )*( x - 2 ) = 0 }}}
{{{ x = 2 }}} ( ignore the negative root )
The border is 2 inches wide
check:
{{{ ( 10+ 2x )*( 8 + 2x ) = 168 }}}
{{{ ( 10+ 2*2 )*( 8 + 2*2 ) = 168 }}}
{{{ 14*12 = 168 }}}
{{{ 168 = 168 }}}