Respuesta :

irspow
20/t=v and 12/t=(v-4)  solve both for t

t=20/v  and t=12/(v-4)  since t=t

20/v=12/(v-4)  cross multiplying...

20v-80=12v

8v-80=0

8v=80

v=10mph

The outbound speed was 10mph