Bài 1 :
a,9/5+2/5x4/6
=9/5 + 8/30
= 62/30=31/50
b,3/8x2-6/7x1/3
= 6/8- 6/21
=13/18
Bài 2:
a, C1:6/7x(2/5+3/10) C2: 6/7x(2/5+3/10)
= 6/7x 7/10 = 6/7x2/5+6/7x3/10
= 42/70=3/5 = 12/35 + 18/70
= 42/70=3/5
b,C1: 2/5x3/7+2/5x4/7 C2:2/5x3/7+2/5x4/7
= 6/35+ 8/35 = 2/5x(3/7+4/7)
= 14/35=2/5 = 2/5 x 7/7
=2/5x1=2/5
CHÚC BẠN HỌC TỐT!!!