Explicação passo a passo:

80 km >>>>>>3 hs/dia >>>>>>>>4 dias

200 >>>>>>> 5 >>>>>>>> >>>>>> x dias

km e dias >>>> diretamente proporcional ( 80/200)

hs/dia e dias >>>>>inversamente ( inverte hs/dia 5/3 )

80/300= 5/3 = 4/x

x = ( 4 * 300 * 3 ) / ( 80 * 5 )

x =3600/400

x =9 dias>>>>>>>>>>resposta