Question 999940
In the thirty minutes before Mark leaves, Nancy drives 17.5 miles.  If they need to be 175 miles apart, they'll need to cover 175-17.5 = 157.5 miles in some time t.
He travels 55t and she travels 35t miles...their sum must be 157.5, so
55t + 35t = 157.5
90t = 157.5
t = 1.75 hours or 1 hour 45 minutes
Thus an hour and 45 minutes after Mark leaves is
11:15 am.