bài 1:a 2+ 5/6 + 7/12= 2/1+ 5/6 + 7/12= 24/12+10/12+7/12=41/12
b 3/5+6 + 9/15=3/5+6/1+9/15=9/15+90/15+9/15=108/15
c 21/27+9 + 12/3= 21/27+ 9/1+12/3= 21/27+252/27+108/27=381/27
d5/6+7/12+2=5/6+7/12+2/1= 10/12+ 7/12+24/12=41/12
bài 2: a 2/12 + 5 + 10/12= 2/12+5/1+10/12=2/12+60/12+10/12=72/12
b 16/20+7/20+13=16/20+7/20=13/1=16/20+7/20+260/20=283/20
c7/12+14/21+9=7/12+14/21+9/1=49/84+56/84+756/84=861/84
d 25/30+7+5/30=(25/30+5/30)+7= 1+7=8
Đủ nha hơi lâu chút :vvv