Need help with this short physics question

Question

there is a race betwen person A and person B. They both start at the same time, but B initial position is 10m left of peron A. person A travels 100 meters right in 20 seonds, Person Btravels 112.5 meters right in 15 seconds.

what is the time, postion and, and person B displacement at which Person B catches up with Person A

Answer 1

Consider person A's starting position to be 0.

for person A, d = r * t
d = 100 meters / 20 sec * t
d = 5 meters / sec * t

for person B, d = 10 + (d * t)
d = 10 + (112.5 meters / 15 sec * t)
d = 10 + (7.5 meters / sec * t)

We know the two positions are equal when person A catches person B. So.

5 meters / sec * t = 10 + (7.5 meters / sec * t)

solving that will give you t.

To find the distance, use the simpler of the 2 original equations:
d = 5 meters / sec * t

Answer 2

i don't get how to find the time