Step-by-step explanation:
Nancy leaves the house at 7:00 A.M. and averages 15 miles per hour. Mark leaves at 7:15 A.M. and averages 60 miles per hour.
Let the time after the start of Mark when they are 135 miles apart be t hours.
Time traveled by Nancy = t + 7:15 - 7:00 = t + 15 minutes = (t+0.25) hours
They are traveling in the opposite direction so,
Distance between them = Speed of Nancy x Time of travel of Nancy + Speed of Nancy x Time of travel of Nancy
135 = 15 x (t+0.25) + 60 x t
135 = 15t + 3.75 + 60t
75t = 131.25
t = 1.75 hours = 1 hour 45 minutes
Time = 7: 15 + 1 hour 45 minutes = 9 : 00 AM
At time 9 : 00 AM they are 135 miles apart.
