Word problem in algebra - two boys, shawn and curtis, went for a walk, shawn began walking 20 seconds earlier than curtis. shawn walked at a speed of 5 feet per second. curtis walked at a speed of 6 feet per second. for how many seconds had shawn been walking at the moment when the two boys had walked the same distance?

So first you should simplify it.
Shawn (S) - 5 ft. per sec
Curtis (C) - 6 ft. per sec
     1 sec        2 s         3 s         4s        5s          6s
S     25 ft       30 ft       35 ft      40 ft      45 ft      50 ft
C     6 ft        12 ft       18 ft      24 ft      30 ft      36 ft
So we keep going on with this table until we find two numbers that match, which is 30. Then we look back at the question. We want to find how many seconds Shawn was at when the hit the same distance as Curtis (30 ft). Yet be sure to keep in mind that Shawn started 20 seconds earlier. So the answer is 2 seconds.