a,2/3 + 4/-5 x 20/16 =-1/3

b,(1/3+4/6).(2/7+9/14)=13/14

c,(2/3 - 3/4).(1/2- -3/5)=-11/120

a,2/3 + 4/-5 x 20/16
=2/3-1
=-1/3
b,(1/3+4/6).(2/7+9/14)
=1.13/14
=13/14
c,(2/3 - 3/4).(1/2- -3/5)
=-1/12.-1/10
=1/120

a) \(\dfrac{2}{3}+\dfrac{4}{-5}\times\dfrac{20}{16}\)\(=\dfrac{2}{3}+\dfrac{-4}{5}\times\dfrac{5}{4}\)\(=\dfrac{2}{3}+\left(-1\right)=-\dfrac{1}{3}\)

b) \(\left(\dfrac{1}{3}+\dfrac{4}{6}\right)\cdot\left(\dfrac{2}{7}+\dfrac{9}{14}\right)\)\(=1\cdot\dfrac{13}{14}=\dfrac{13}{14}\)

c) \(\left(\dfrac{2}{3}-\dfrac{3}{4}\right)\cdot\left(\dfrac{1}{2}-\dfrac{-3}{5}\right)\)\(=-\dfrac{1}{12}\cdot\dfrac{11}{10}=-\dfrac{11}{120}\)

Ko hiểu đề bài

\(2\frac{1}{6}x3+3\frac{4}{5}x10x9\frac{1}{10}\)

\(=1+38x9\frac{1}{10}\)

\(=1+345,8\)

\(346,8\)

Giải:

\(\frac{1+3x}{6}-\frac{2+x}{9}=-4+x\)

\(\text{⇔}\frac{3+9x}{18}-\frac{4+2x}{18}=-\frac{72}{18}+\frac{18x}{18}\)

\(\text{⇔}3+9x-4+2x=-72+18x\)

\(\text{⇔}3+9x-4+2x+72-18x=0\)

\(\text{⇔}71-7x=0\)

\(\text{⇔}x=\frac{71}{7}\)

Vậy...

Chúc bạn học tốt@@

a)x+x+2.x=76:2

=>2x+2x=38

=>2(x+x)=38

=>2x=19

=>x=19/2

b)2.x=x+14

=>2x-x=14

=>x=14

c)2.x-3/5=3/4

=>2x=3/4+3/5

=>2x=27/20

=>x=27/40

d)3/5-2.x=1/4

=>2x=3/5-1/4

=>2x=7/20

=>x=7/40

1, 

Với x=-24 ta có

(-90)-(x+10)+100

= (-90)-(-24+10)+100

= -90+24-10+100

= (100-90)+(24-10)

= 10+14

= 24

2,

Với x=4, y=-9 ta có

[(-25).(-27).(-x)]:y

= [(-25).(-27).(-4)]:(-9)

= [(-25).(-4).(-27)]:(-9)

= [100.(-27)]:(-9)

= (-2700):(-9)

= 300

3,

Với a=-15, b=2019 ta có

a-b+17+8.(-3)+b

= (-15)-2019+17+8.(-3)+2019

= (-15)-2019+17+(-24)+2019

= (-15)-2019+17-24+2019

= (17-15)+(2019-2019)-24

= 2-24

= -22

Ta có:x+3/4=-9/x+3

<=>x+9/x=3-3/4

<=>(x²+9)/x=9/4

<=>4x²+36=9x

<=>x(4x-9)=-36

bài này x thuộc Z từ đó xét bảng gt

\(\frac{x+3}{4}=\frac{-9}{x+3}\)

\(\Rightarrow\left(x+3\right)^2=-36\)

=> Ko tìm được x thỏa mãn