`@` `\text {Ans}`

`\downarrow`

`(25 \times 35) \times 40`

`= 25 \times 40 \times 35`

`= 1000 \times 35`

`= 35000`

`(25×35)×40`

`=25×35×40`

`=(25×40)×35`

`=1000×35`

`=35000`

a=(32*125)*9=4000*9=36000

b=768*(105-4-1)=768*100=76800

36000

76800 tck nha!

A :36000

B :78336

`Answer:`

\(A=\frac{8}{9}.\frac{15}{16}.\frac{24}{25}.\frac{35}{36}.\frac{48}{49}.\frac{63}{64}\)

\(=\frac{8.15.24.35.48.63}{9.16.25.36.49.64}\)

\(=\frac{2^3.3.5.2^3.3.5.7.2^4.3.3^2.7}{3^2.2^4.5^2.2^2.3^2.7^2.2^6}\)

\(=\frac{3}{2^2}\)

\(=\frac{3}{4}\)

`3/4 xx  8/9 xx 15/16 xx 24/25 xx 35/36`

`= (3xx8xx15xx24xx35)/(4xx9xx16xx25xx36)`

`=(3xx4xx2xx5xx3xx4xx6xx7xx5)/(4xx3xx3xx4xx4xx5xx5xx6xx6)`

`=(2xx7)/(4xx6)`

`=(2xx7)/(2xx2xx6)`

`=7/12`

\(\dfrac{3}{4}\times\dfrac{8}{9}\times\dfrac{15}{16}\times\dfrac{24}{25}\times\dfrac{35}{36}\)

= \(\dfrac{3\times8\times15\times24\times35}{4\times9\times16\times25\times36}\)

= \(\dfrac{3\times\left(2\times4\text{​​}\text{​​}\right)\times\left(3\times5\right)\times\left(6\times4\right)\times\left(5\times7\right)}{4\times\left(3\times3\right)\times\left(4\times4\right)\times\left(5\times5\right)\times\left(6\times6\right)}\)

=\(\dfrac{2\text{​​}\text{​​}\times3\times6\times\left(5\times7\right)}{3\times4\times5\times\left(6\times6\right)}\)

=\(\dfrac{\text{​​}\text{​​}7}{2\times6}\)= \(\dfrac{7}{12}\)

BẠN ƠI ! ĐỀ ĐÚNG KHÔNG VẬY ???????????

a,21x6+18x6+6x61

=6x(21+18+61)

=6x100

=600

b,1078x25-25x35-43x25

=25x(1078-35-43)

=25x1000

=25000

c,74x18+740x6+22x74

=74x18+74x10x6+22x74

=74x18+74x60+22x74

=74x(18+60+22)

=74x100

=7400

a, 25+35+76+65+22
=(65+35)+(76+22)+25
=100+100+25
=225
c , 78-23-25
=78-(23+25)
=78-48
=30
a , x-45=20 
x=20+45
x=65
b , 45 - x=20
     x =45-20
     x= 25

Bài 2: 

a: Ta có: x-45=20

nên x=65

b: Ta có: 45-x=20

nên x=25