Bài 13:
a)
= -283/693 . 7/4 + 7/4 . 97/99
= 7/4 . (-283/693 + 97/99)
= 7/4 . 4/7
= 1
b)
= 5/8 - 3/8 . (-4/3) - 0
= 5/8 - (-1/2) - 0
= 9/8
c)
= 5/2 - 1 + 1/9 . (-1/3)
= 5/2 - 1 + (-1/27)
= 79/54
d)
= (3/4 - 2/5) : (-5/3 + 3)
= 7/20 : 4/3
= 7/20 . 3/4
= 21/80