Question 758858
Let {{{ t }}} = time for trip in hrs while driving
Average speed = ( total distance ) / ( total time )
Average speed = {{{ 78 }}} km/hr
Total distance = {{{ 94t }}}
Total time = {{{ t + 80/60 }}} 
Total Time = {{{ t + 4/3 }}}
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Now I can say:
Average speed = {{{ ( 94t ) / ( t + 4/3 ) }}}
{{{ 78 = ( 94t ) / ( t + 4/3 ) }}}
{{{ 78*( t + 4/3 ) = 94t }}}
{{{ 78t + 104 = 94t }}}
{{{ 16t = 104 }}}
{{{ t = 6.5 }}}
The time spent driving is {{{ 6.5 }}} hrs
{{{ d = 94t }}}
{{{ d = 94*6.5 }}}
{{{ d = 611 }}}
The trip is 611 miles
check:
Average speed = ( total distance ) / ( total time )
{{{ 78 = 611 / ( 6.5 + 4/3 ) }}}
{{{ 78*7.8333 = 611 }}}
{{{ 611 = 611 }}}
OK