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A = 8/7 + 5/7 x 1/15

A = 8/7 + 5/105

A = (8 x 15) / (7 x 15) + 5/105

A = 120/105 + 5/105

A = 125/105

A = (5 x 25) / (5 x 21)

A = 25/21.

B = 4/9 - 8/9 : 16/5

B = 4/9 - 8/9 x 5/16

B = 4/9 - 40/144

B = (4 x 16) / (9 x 16) - 40/144

B = 64/144 - 40/144

B = 24/144

B = (24 x 1) / (24 x 6)

B = 1/6

C = (7/4 - 2) : (5/4 + 3)

C = [7/4 - (2 x 4) / (1 x 4)] : [5/4 + (3 x 4) / (1 x 4)]

C = (7/4 - 8/4) : (5/4 + 12/4)

C = - 1/4 : 17/4

C = - 1/4 x 4/17

C = - 4/68

C = (4 x - 1) / (4 x 17)

C = - 1/17

D = (5 - 2/5) : (4/5 + 9)

D = [(5 x 5) / (1 x 5) - 2/5] : [4/5 + (9 x 5) / (1 x 5)]

D = (25/5 - 2/5) : (4/5 + 45/5)

D = 23/5 : 49/5

D = 23/5 x 5/49

D = 115/245

D = (5 x 23) / (5 x 49)

D = 23/49.