gary has walked 305 meters, and continues at a rate of 1 meter per second. Mary has walked 113 meters, and continues at a rate of 3 meters per second. In how many seconds will they have traveled the same distance.

let the addition time be t seconds

Gary went 305 + (1)t
Mary went 113 + 3t

113 + 3t = 305 + t
2t = 192
t = 96

after 96 seconds each one has gone 401 m