Problem: a man can row his boat with the stream at 30 km / h and against the stream in 14 km / h . the man ' s rate is ?
Rationale: "ds = 30 us = 14 s = ? s = ( 30 - 14 ) / 2 = 8 kmph answer : e"
annotated_formula: divide(subtract(30, 14), const_2)