a ) Cách 1 : b) Cách 1 :
( 6/11 + 5/11 ) x 3/7 3/5 x 7/9 - 3/5 - 2/9
= 1 x 3/7 = 7/15 - 3/5 - 2/9
=3/7 =7/15 - 9/15 - 2/9
Cách 2 : = - 2/15 - 2/9 = - 16/45 ( 6/11 + 5/11 ) x 3/7 Cách 2 :
= 6/11 x 3/7 + 5/11 x 3/7 3/5 x 7/9 - 3/5 - 2/9
= 18/77 + 15/77 = 7/15 - ( 3/5 + 2/9 )
= 33/77 = 7/15 - 37/45
= 3/7 = - 16/45
a)6/11+5/11)x3/7=1x3/7=3/ b)3/5x7/9-3/5-2/9=3/5x7/9--2/9=3/5x7/9+2/9=3/5x1=3/5