Let's write some equations.
Mingwei's distance from Town A after
hours from 8:00 is
.
Ali's distance from Town B after
hours is
, since he doesn't start walking for 40 minutes.
When Mingwei's distance is twice Ali's, they've met up (since their distance from Town A is twice their distance from Town B).
So, this gives
, so
, so
, so the time is 10:40.
After
hours, Mingwei has traveled
kilometers while Ali has traveled sixty, so the distance between the towns is
kilometers.