How do I set up and solve this problem Linda drove from Phil

How do I set up and solve this problem? Linda drove from Philadelphia to NYC at the rate of 50 miles per hour. She made the trip from NYC to Philadelphia at the rate of 40 miles per hour. She drove the same route both ways. Her total driving time was 3.6 hours. Find the number of hours she drove from Philadelphia to NYC. Hint: Let x be the number of hours from Philadelphia to NYC.

Solution

This is an RTD question. Here is a table based on the given information
travel . . . . . . . .rate . . . . . . . . . . time . . . . . . . . . distance
to NYC . . . . . . .50. . . . . . . . . . . . x. . . . . . . . . . . . .50x
to Phila . . . . . . 40. . . . . . . . . . . . 3.6 - x. . . . . . . . 144 - 40x
total . . . . . . . . . . . . . . . . . . . . . . 3.6 . . . . . . . . . . . . . .
since distance is the same, we get
50x = 144 - 40x
add 40x to get
90x = 144
divide to get
x = 1.6 hours to NYC