The 3rd answer, when m is next to a number it means “per” for something like per second or (in this case) per minute, etc...
Speed is distance over time. There’s no distance in the question and the time is 1 hr 30 mins hence 1.5 hours.
Answer:
angle 2 = 90° {corresponding angles}
angle 7 + angle 5 = 180° {linear pair}
or, angle 7 + 100° = 180° {angle 5 is corresponding to 100°}
so, angle 7 = 80°
