a: =>x=1135:37=1135/37

b: =>3x=165

hay x=55

c: =>x-8=92

hay x=100

\(a,x=1135:37=30\left(dư.27\right)\\ b,x\times3=40755:247=165\\ x=165:3=55\\ c,x-8=57316:623=92\\ x=92+8=100\)

a: \(\Leftrightarrow x\cdot12.71=1.269\)

hay x=1269/12710

đầy đủ giúp e ak

\(a)3,14\times\dfrac{1}{4}+3,14\times99+3,14\times75\%\\ =3,14\times0,25+3,14\times99+3,14\times0,75\\ =3,14\times\left(0,25+99+0,75\right)\\ =3,14\times100\\ =314\)

\(3,14\cdot\dfrac{1}{4}+3,14\cdot99+3,14\cdot75\%\)

\(=3,14\cdot0.25+3,14\cdot99+3,14\cdot0.75\)

\(=3,14\cdot\left(0.25+99+0.75\right)\)

\(=3,14\cdot100\)

\(=314\)

a: \(\Leftrightarrow x\cdot12.71=1.269\)

hay x=1269/12710

3,14x\(\frac{4}{5}\)=2,512

\(2\frac{1}{2}x2x3,14=15,7\)

3,14x4/5=2,512

2/1/2x2x3,14=15,7

A) - 2);    B) - 5);    C) - 4);    D) - 3)

(Lưu ý: B có thể nối với 2) hoặc với 4).

\(1+\left(1+2\right)+\left(1+2+3\right)+\left(1+2+3+4\right)+...+\left(1+2+3+...+100\right)\)

\(=\left(1+1+1+...+1\right)+\left(2+2+...+2\right)+\left(3+..+3\right)+...+\left(99+99\right)+100\)

( biểu thức trên có 100 số 1, 99 số 2, 98 số 3,...., 2 số 9, 1 số 100)

\(=100\times1+99\times2+98\times3+...+2\times99+1\times100\)

suy ra \(\frac{1+\left(1+2\right)+\left(1+2+3\right)+\left(1+2+3+4\right)+...+\left(1+2+3+...+100\right)}{100\times1+99\times2+98\times3+...+2\times99+1\times100}=1\)

\(0,25\times3,14+3,14\div4-3,14\times0,5\)

\(=0,25\times3,14+3,14\times0,25-3,14\times0,5\)

\(=3,14\times\left(0,25+0,25-0,5\right)\)

\(=3,14\times1=3,14\)

( 1/2 - 1/3 + 3/4 ) : ( 2/5 - 1/x ) = 2,5

11/12  : ( 2/5 - 1/x ) = 2,5

2/5 - 1/x  = 11/12 : 2,5

2/5 - 1/x = 11/30 

        1/x = 2/5 - 11/30

        1/x = 1/30

=> x = 30