Mỗi phần đúng được (0,75đ)

a) 76 + x = 257

             x = 257 – 76

             x = 181

b) 672 : x = 6

              x = 672 : 6

              x = 112

a= 257 x (87+23)
=257 x 100 
=25700
b=712 x (25+74)+752
=75200
c=94100

Chuẩn luôn rồi 
Học tốt

a) 102 + x = 257

               x = 257 – 102

               x = 155

b) 500 – x = 100

               x = 500 – 100

               x = 400

x * 257 + x = 4644

x * 257 + x * 1 = 4644

x * (257 + 1)    = 4644

x * 258            = 4644

x                     = 4644 : 258

x                     = 18

Sửa đề: \(\frac{x+1}{156}+\frac{x+2}{155}+\frac{x+3}{154}+\frac{x+247}{30}=0\)

=>\(\frac{x+1}{156}+1+\frac{x+2}{155}+1+\frac{x+3}{154}+1+\frac{x+247}{30}-3=0\)

=>\(\frac{x+157}{156}+\frac{x+157}{155}+\frac{x+157}{154}+\frac{x+157}{30}=0\)

=>x+157=0

=>x=-157

Sửa đề: \(\frac{x+1}{156}+\frac{x+2}{155}+\frac{x+3}{154}+\frac{x+247}{30}=0\)

=>\(\frac{x+1}{156}+1+\frac{x+2}{155}+1+\frac{x+3}{154}+1+\frac{x+247}{30}-3=0\)

=>\(\frac{x+157}{156}+\frac{x+157}{155}+\frac{x+157}{154}+\frac{x+157}{30}=0\)

=>x+157=0

=>x=-157

Bạn ơi ghi đề sai nha ban phải là: 257 x 135 - 34 x 257 - 257 nha

257 x 135 - 34 x 257 - 257 x 1

= 257 x ( 135 - 34 -1 )

= 257 x 100

=25700

\(c,257-\left(x^2-1\right)=177\\ \Rightarrow x^2-1=80\\ \Rightarrow x^2=81\\ \Rightarrow\left[{}\begin{matrix}x=-9\\x=9\end{matrix}\right.\)

Tks bạn nhiều nhoaaa