\(a,123\times54+27\times123-12\times123+123\times31\)

\(=123\times\left(54+27-12+31\right)\)

\(=123\times100\)

\(=12300\)

\(b,\dfrac{121}{27}\times\dfrac{54}{11}< n< \dfrac{100}{21}:\dfrac{25}{126}\)

\(22< n< \dfrac{100}{21}\times\dfrac{126}{25}\)

\(22< n< 24\)

Vì \(23>22\) và \(23< 24\) nên \(n=23\)

a, 123x(54+27-12+31)

=123x100

=12300

a123x54+27x123-12x123+123x31

=123:54+27:123-12:123+123:31

=6642+27:123-12:123+123:31

=6642+3321-12:123+123:31

=6642+3321-1476+123:31

=6642+3321-1476+3813

=12300

b,121/27x54/11<n>100/21:25/126

=22<n>24

n=23

1¹=1

123 x 10 = 1230

11²=121

123 + 0 = 123

1¹=1

123x10=1230

11²=121

123+0=123

\(1^1=1\)

\(123.10=1230\)

\(11^2=121\)

\(123+0=123\)

\(nha^{ }\)

= 1353 

123.11=123.10+123=1230+123=1353

123 x 11 = 

1353

Bằng 255

k nha

155 nhé

12x11+123

=132+123

=255

11 + 22 + ( \(x\) x 2 + \(x\) x 199 ) : 33 = 123 x 123

                 33 + \(x\) ( 2 + 199) : 33  = 15129

                                    201\(x\) : 33  = 15129 - 33

                                    201\(x\) : 33 = 15096

                                    201\(x\)        = 15096 x 33

                                    201\(x\)        = 498168

                                          \(x\)        = 498168 : 201

                                          \(x\)        = 166056/67

a) \(3119\cdot121-3119\cdot11\cdot11\)

\(=3119\cdot121-3119\cdot\left(11\cdot11\right)\)

\(=3119\cdot121-3119\cdot121\)

\(=3119\left(121-121\right)\)

\(=0\)

b) \(24\cdot\left(123\cdot87\right)+\left(87\cdot123\right)\cdot76\)

\(=\left(123\cdot87\right)\cdot\left(76+24\right)\)

\(=\left(123\cdot87\right)\cdot100\)

\(=1070100\)

\(\Leftrightarrow\dfrac{5}{4}\left(\dfrac{4}{3\cdot7}+\dfrac{4}{7\cdot11}+...+\dfrac{4}{x\left(x+4\right)}\right)=\dfrac{50}{123}\)

=>(1/3-1/7+1/7-1/11+...+1/x-1/x+4)=50/123:5/4=50/123*4/5=40/123

=>1/3-1/x+4=40/123

=>1/x+4=1/123

=>x+4=123

=>x=119