Hi there..

i've got my own solution but i'm not so sure if this correct..

if Local train will be arrived in x hour then Express train will be arrived in x-2 hour (2 hours ahead).

let speed of Local train be L=60/x---------------1

let speed of Express train be 2L=60/(x-2)--------2

substitutes 1 into 2 and i got x=4

speed of local train will be 15miles/h and express train will be 30miles/h