a: \(245\times11+11\times365\)

=11x(245+365)

=11x610

=6710

b: \(78\times75+75\times89+75\times123\)

\(=75\times\left(78+89+123\right)\)

=75x290

=21750

c: \(2\times250\times50\times8\)

=2x50x250x8

=100x2000

=200000

d: (76:7)x4

=76x4:7

=304/7

e: (372x15)x9

=5580x9

=50220

f: (56x23x4):7

=56:7x23x4

=8x92

=736

Bài 3:

a: Ta có: \(23\left(42-x\right)=23\)

\(\Leftrightarrow42-x=1\)

hay x=41

b: Ta có: 15(x-3)=30

nên x-3=2

hay x=5

Bài 1: 

a: 32+89+68=100+89=189

b: 64+112+236=300+112=412

c: \(1350+360+650+40=2000+400=2400\)

\(\frac{x+22}{11}+\frac{x+23}{12}=\frac{x+24}{13}+\frac{x+25}{14}\)

\(\Leftrightarrow\left(\frac{x+22}{11}+1\right)+\left(\frac{x+23}{12}+1\right)=\left(\frac{x+24}{13}+1\right)+\left(\frac{x+25}{14}+1\right)\)

\(\Leftrightarrow\frac{x+33}{11}+\frac{x+35}{12}=\frac{x+37}{13}+\frac{x+39}{14}\)

\(\Leftrightarrow\frac{x+33}{11}+\frac{x+35}{12}-\frac{x+37}{13}-\frac{x+39}{14}=0\)

\(\Leftrightarrow\frac{2184\cdot\left(x+33\right)+2002\cdot\left(x+35\right)-1848\cdot\left(x+37\right)-1716\cdot\left(x+39\right)}{24024}=0\)

\(\Leftrightarrow2184x+72072+2002x+70070-1848x-68376-1716x-66924=0\)

\(\Leftrightarrow622x+6842=0\)

\(\Leftrightarrow x=-11\)

Ta có: \(\frac34\times36+75\%\times23+\frac{75}{100}+0,75\times40\)

\(=0,75\times36+0,75\times23+0,75+0,75\times40\)

\(=0,75\times\left(36+23+1+40\right)=0,75\times100=75\)

a) 6x + 15 = 75

6x = 75 - 15

6x = 60

x = 60 : 6

x = 10

b) x - 12 = (-27)

x = (-27) + 12

x = -15

c) 23 + (x - 5) : 4 = 3⁸ : 3⁵

23 + (x - 5) : 4 = 3³

23 + (x - 5) : 4 = 27

23 + (x - 5) = 27 x 4

23 + (x - 5) = 108

x - 5 = 108 - 23

x - 5 = 85

x = 85 + 5

x = 90

= 89 x ( 23 - 17 + 4 )

= 89 x 10

= 890

=  89.(23 - 17 + 4)

= 89.10

= 890

1: \(=75\left(27+25-2\right)=75\cdot50=3750\)

2: \(=15\left(23+37\right)+55=15\cdot60+55=955\)

3: \(=36\cdot14+36\cdot17+36\cdot69\)

\(=36\cdot100=3600\)

4: \(=200\cdot\left(32+68\right)=200\cdot100=20000\)

\(a,C=2^3\cdot3-\left(1^{10}+15\right):4\)

\(=8\cdot3-16:4\)

\(=24-4\)

\(=20\)

\(Vậy : C=20\)

\(b,\left(75:3+2\cdot9^2\right):x=11\)

\(\Rightarrow\left(25+162\right):x=11\)

\(\Rightarrow187:x=11\)

\(\Rightarrow x=187:11\)

\(\Rightarrow x=17\)

\(Vậy: x=17\)

#\(Toru\)

Lời giải:
a.

$(x-15).27=0$

$x-15=0:27=0$

$x=15+0=15$

b.

$23(42-x)=0$

$42-x=0$

$x=42$

c.

$(9x+2).3=60$

$9x+2=60:3=20$

$9x=18$

$x=2$
d.

$71+(26-3x):5=75$

$(26-3x):5=75-71=4$

$26-3x=4.5=20$

$3x=26-20=6$

$x=6:2=3$