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A= 3/10 + -5/5

A = 3/10 - (5 x 2) / (5 x 2)

A = 3/10 - 10/10

A = - 7/10

B= 28/36 - 9/4

B = 28/36 - (9 x 9) / (4 x 9)

B = 28/36 - 81/36

B = - 53/36

C= -5/21 + 3/7

C = - 5/21 + (3 x 3) / (7 x 3)

C = - 5/21 + 9/21

C = 4/21

D= 11/12 - 5/4

D = 11/12 - (5 x 3) / (4 x 3)

D = 11/12 - 15/12

D = - 4/12

D = (4 x - 1) / (4 x 3)

D = - 1/3

E= -7/10 + 3/4

E = (- 7 x 2) / (10  x 2) + (3 x 5) / (4 x 5)

E = - 14/20 + 15/20

E = 1/20.