215-5.( x-9) = 195

       5.( x-9) = 215 - 195

      5. ( x-9) = 20

          x-9 = 20:5 

          x-9 = 4

         x      = 4+9

        x       =  13

\(A=\left(6888:56-11^2\right).152+13.72+13.28\)

\(A=\left(6888:56-121\right).152+13.72+13.28\)

\(A=\left(123-121\right).152+13.72+13.28\)

\(A=2.152+13.72+13.28\)

\(A=13.\left(72+28\right)+152.2\)

\(A=1300+304\)

\(A=1604\)

\(B=\left[5082\right]\left(17^{29}:17^{27}-16^2\right)+13.12\left[\right]:31+9^2\)

\(B=\left[5082\left(17-16^2\right)15.6\right];31+81\)

\(B=310:31+81\)

\(B=10+81\)

\(B=91\)

A=1604

B=91

em chưa học mà

    5 x ( 2x + 3 ) -7x = 0

= 10x + 15 - 7x = 0

= 10x - 7x +15 =0

=  3x + 15 = 0

=   3x  = -15

=     x = -5

HT

BCNN(280)=\(^{2^2\times5\times7=140}\)

BCNN\(\left(280\right)=2^2\times5\times7=140\)

\(=\frac{99999\cdot\left(99999+1\right)}{2}\)

\(=\left(99999\cdot100000\right):2=99999\cdot100000:2\)

\(=99999\cdot50000=4999950000\)

Vậy A = 4999950000

\(26\times5^{x-1}-5^{x-1}=125\)

\((26-1)\times5^{x-1}=125\)

\(5^2\times5^{x-1}=5^3\)

\(5^{x-1}=5^3\div5^2\)

\(5^{x-1}=5\)

\(\Rightarrow x-1=1\)

\(x=1+1=2\)

      26 x 5^x-1 - 5^x-1 = 125

26 x 5^x-1 - 5^x-1 x 1=125

( 26 - 1 ) x 5^x-1       =125

        25  x   5^x-1      =125

                        5^x-1=125 : 25

                       5^x-1 = 5

                        5^x-1= 5¹

            => x - 1      = 1

                    x         =  1 + 1

                            x = 2

Vậy x = 2

( học tốt nhé! )