Question 1027456
Let {{{ h }}} = her time for the whole trip
{{{ h - 5 }}} = her time for the 2nd part of the trip
--------------------
Let {{{ d }}} = her distance in miles for 2nd part of the trip 
{{{ d = 50*( h - 5 ) }}}
--------------------
Her average speed for the whole trip is:
[ total distance ] / [ total time ]
{{{ f(h) = ( 300 + 50*( h - 5 ) ) / h }}}
{{{ f(h) = ( 300 + 50h - 250 ) / h }}}
{{{ f(h) = ( 50h + 50 ) / h }}}
{{{ f(h) = 50 + 50/h }}}
--------------------
Maybe I read this wrong -get another opinion, too