A= -15/7 x 14/25.  B= 18x7/27.  C= -15/28 x 21/20.  D= 13/-45 x -18/26.  E= 77/49 x 35/-121. F= -54/81 x -63/-42.

A =  - 15/7 x 14/25
A = - 210/175
A = 35 x - 6 / 35 x 5
A = - 6/5

B = 18 x 7/27
B = 126/27
B = 9 x 14 / 9 x 3
B = 14/3

C =  - 15/28 x 21/20
C = - 315/560
C = 35 x - 9 / 35 x 16
C = - 9/16

D = 13/- 45 x -18/26
D = 234/1170
D = 234 x 1 / 234 x 5
D = 1/5

E = 77/49 x 35/- 121
E = - 2695/5929
E = 539 x - 5 / 539 x 11
E = - 5/11


F = -54/81 x -63/-42
F = - 3402/3402
F = - 1