Question 1203782

if {{{ E}}} is the midpoint of {{{ DF}}}, then {{{ DE=EF}}}

if

{{{ DE = 4x + 3}}}
{{{ EF = 8x - 9}}}

then

{{{ 4x + 3=8x - 9}}}
{{{ 9+ 3=8x -4x }}}
{{{ 12=4x }}}
{{{ x=3}}}


so,

{{{ DE = 4x + 3=4*3+3=15}}}
since{{{ DE=EF}}}, we have {{{EF =15}}}

{{{ DE=EF+DF=DE+EF =15+15=30}}}