Question

[nguyen tran khanh huyen]

Tinh nhanh 

A= -7/21 +(1+1/3)

B= 2/15 +(5/9+-6/9)

C= (-1/5+3/12)+-3/4

Answer 1

[Nguyễn Hoàng Tùng]

A=-7/21 + (1+1/3)

=-1/3 + 1 + 1/3

=(1/3 + 1/3) +1

=2/3 +1

=2/3 + 3/3

=5/3

B=2/15 + (5/9 + -6/9)

=2/15 + -1/9

=6/45 + 5/45

=11/45

C=(-1/5 + 3/12) + -3/4

=-1/5 + (1/4 + -3/4)

=-1/5 + -1/2

=2/10 + -5/10

=3/10

k cho mik nha

Answer 2

[Nguyễn Thị Ngọc Oanh]

A= -7/21 +(1+1/3) = 1

B= 2/15 +(5/9+-6/9) = 61/45C= (-1/5+3/12)+-3/4 = -7/10