Two planes leave New York at 10 am one heading for Europe at

Two planes leave New York at 10 a.m., one heading for Europe at 900 km/h and one heading in the opposite direction at 300 km/h. At what time will they be 1 400 kn apart? How far has each traveled?

Solution

900x+300x=1,400
1,200x=1,400
x=1,400/1,200
x=1.167 hours they will be 1,400 km. apart.
proof:
900*1.167+300*1.167=1,400
1050+350=1,400
1,400=1,400