-5/9.7/13+6/13.5/9+3 7/9
= 5/9.(-7/13) + 6/13.5/9 + 34/9
= 5/9.(-7/13+6/13) + 34/9
= 5/9.(-1/13)+ 34/9
= -5/117 + 34/9
= 437/117
cau 2 : 6 3/8 -(4 3/8 -1/2)
= 51/8 - (35/8 - 1/2)
= 51/8 - 31/8
= 5/2
cau 3 :2 1/3.1,5-(11/10+50%):4/15
= 7/3.3/2 - (11/10+ 1/2) : 4/15
= 21/6 - 8/5 :4/15
= 21/6 - 6
= -5/2