At 10a. m. juan leaves the city traveling north at 60 mi/hr. one hour later mel leaves the city traveling south at 50 mi/hr. at what time will they be 830 miles apart?

-- At 11 AM, when Mel starts out, Juan has already covered 60 miles.

-- After that, since they're traveling in opposite directions, the distance
between them increases (60 + 50) = 110 miles every hour.

Let's call 'H' the number of hours after 11 AM.
Then the distance between them is

D = 110H + 60

When is this distance 830 miles ?  Wouldn't you like to know !

830 = 110H + 60

Subtract 60 from each side:

770 = 110H

Divide each side by 110 :

H = 770 / 110 = 7 .

It happens 7 hours after 11 AM.
That would be 6:00 PM .