Question 512029
 {{{ -28=-4sqrt (r+8)}}}
By looking at it, I see that {{{ sqrt( r + 8 ) }}}
must equal {{{ 7 }}}
Then I have {{{ -28 = -28 }}}
{{{ sqrt( r + 8 ) = 7 }}}
Square both sides
{{{ r + 8 = 49 }}}
{{{ r = 41 }}}