Two cyclist start on a circular track from a given point but in opposite direction with speeds of 7m/s and 8m/s. If the circumference of the circle is 180meters, after what time will they meet at the starting point? Choose the correct choice from the following answers:
A) 20 sec  B) 12 sec  C) 30 sec  D) 50 sec  E) 1 min

Rationale: "they meet every 180 / 7 + 8 = 12 sec answer is b"
Answer: B