A, 6/7×8/13+6/13×9/7-3/13×6/7
= 6/7 x (8/13 - 3/13) +6/13×9/7
= 6/7 x 5/13 + 54/91
= 30/91 + 54/91
= 12/13
B, -1/4×152/11+63/4×(-1/11)
= -38/11 - 63/44
= -152/44 - 63/44
= -215/44
C, -9/25×53/3-(-3/5)^2×22/3
= -9/25×53/3 - 9/25 x 22/3
= 9/25 x (-53/3 - 22/3)
= 9/25 x (-25)
= -9
Đ, -21/10+21/10×3/4-3/4
= -21/10+ 63/40 - 3/4
= -51/40