Đáp án:a)35/6, b)4193/261 c)-7/36 d)7/80
Giải thích các bước giải:
a)3/2.7/3+14/3.1/2
=7/2+7/3
=21/6+14/6
=35/6
b)1/9.145-13/3.2/145+2/145
=145/9-2/145(13/3-1)
=145/9-2/145.10/3
=145/9-4/87
=4205/261-12/261
=4193/261
c)(-31/12):15/7-1/18:15/7+20/9:15/7
=((-31/12)-1/18+20/9):15/7
=((-93/36-2/36+80/36).7/15
=(-5/12).7/15
=-7/36
d),7/80;(-7/3)-2/9:(8-8/3)-5/24.(-10/3+38/15)
=7/80.(-3/7)-2/9:(24/3-8/3)-5/24.(-50/15+38/15)
=(-3/80)-2/9:16/3-5/24.4/5
=(-3/80)-2/9.3/16-(-1/6)
=(-3/80)-1/24-(-1/6)
=(-9/240)-10/240-(-40/240)
=7/80
