Arthur and betty start walking toward each other when they are 100m apart. arthur has a speed of 3.0m/s and betty has a speed of 2.0m/s. how long does it take for them to meet?

Let t be the time they both meet. when they meet they both have covered the distance between them .

arthur with 3 m/s would have covered 3t m

Betty with 2 m/s would have covered 2t m

3t + 2t = 100
5t =100
t = 100/5
t= 20 seconds

spot who is helplessly running back and forth
at 5 m/s would have done for 20 seconds.
the distance covered by spot 5 m/s * 20s = 100m

hope this helps hun