2/5*-3/7-1/6*3/2+1/14*2/5

2/5-3/7 - 1/6*3/2 + 1/14*2/5 =

14/35-15/35 - 3/12 + 2/70 =
-1/35 - 1/4 + 1/35 = -1/4.