Answer:
7:45
Step-by-step explanation:
Since they both turn red at differnt times, you have to find a multiple to find the time they will be both on
Main St: 7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, 91, 98, 105
Elm St. 15, 30, 45, 60, 75, 90, 105
They will both turn on 105 minutes or 1 hour and 45 minutes from 6
6 + 1 hr 45 min = 7:45
