Christopher's best time in a race is four seconds faster than his second-best time. His second-best time is 1 1/3 times slower than his best time. Find his

Second Best = Best + 4 sec    (1)

(4/3)Best  =  Second Best  (2)

Sub (1) into (2)

(4/3)Best  =  Best + 4

(1/3)Best  = 4

Best  = 12  seconds

Second Best  = (4/3)Best  =  (4/3)12  =  48/3   = 16 seconds