Question 1017201
Flying X miles at 320M/H should be shown as 

{{{(X miles)(1 hour/320miles)}}} as the above will give time as a result, i.e {{{(X/320) hours}}}

Since the distance is the same, the return trip was

{{{(X miles)(1 hour/280miles)}}} as the above will give time as a result, i.e {{{(X/280) hours}}}

and 

{{{((X/320) hours)+((X/280) hours)=3}}}

multiply thru by 2240

{{{((2240X/320) hours)+((2240X/280) hours)=6720}}}


{{{((7X))+((8X))=6720}}}

{{{(15X)=6720}}}

X= 448

The distance each way was 448 miles. 

{{{(448 miles)(1hr/320miles)=1.4hrs}}}

Note, the average speed is not 300. Half the distance was spent at 320, half at 280, but not half the time.