a) 75% x X+ 3/4 = 30

              75%x X= 30-3/4

              75%x X=117/4

                        X=117/4 : 75/100

                        X=117/4 x 100/75

                        X= 39

75%* X+3/4*X+X=30

3/4*X+3/4*X+X=30

(3/4+3/4+1)*X=30

10/4*X=30

X=30:10/4                   X=12 

3/4 x X + 3/4 x X + X x 1 = 30

X x ( 3/4 + 3/4 + 1 ) = 30

X x 5/2 = 30

X = 30 : 5/2

x= 12

Vậy x = 12

KHÓ QUÁ

 \(75\%\times x+\frac{3}{4}\times x+x=30\)

\(\frac{3}{4}\times x+\frac{3}{4}\times x+x\times1=30\)

\(\left(\frac{3}{4}+\frac{3}{4}+1\right)\times x=30\)

\(\frac{5}{2}\times x=30\)

\(x=30\div\frac{5}{2}\)

\(x=\frac{30\times2}{5}\)

\(x=\frac{60}{5}=12\)

Vậy x = 12

a) \(75\%\times x+\frac{3}{4}\times x+x=30\)

\(\frac{3}{4}\times x+\frac{3}{4}\times x+x=30\)

\(x\times\left(\frac{3}{4}+\frac{3}{4}+1\right)=30\)

\(x\times\frac{5}{2}=30\)

\(x=30\div\frac{5}{2}\)

\(x=30\times\frac{2}{5}\)

\(x=12\)

b) \(x-40\%=36\)

\(x-\frac{2}{5}=36\)

\(x=36+\frac{2}{5}\)

\(x=36\frac{2}{5}\)

c) \(30\%\times x+x=52\)

\(\frac{3}{10}\times x+x=52\)

\(x\times\left(\frac{3}{10}+1\right)=52\)

\(x\times\frac{13}{10}=52\)

\(x=52\div\frac{13}{10}\)

\(x=40\)

\(=\dfrac{3}{4}\left(1+29+30+40\right)=\dfrac{3}{4}\cdot100=75\)

=75

 \(\frac{75}{100}+\frac{3}{4}\times29+75\%\times30+0,75\times40\)

\(=0,75+0,75\times29+0,75\times30+0,75\times40\)

\(=0,75\times(1+29+30+40)\)

\(=0,75\times100\)

\(=75\)

(75 / 100) + ((3 / 4) x 29) + (75% x 30) + (0,75 x 40) =

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75%  x X + 3/4 x X + X = 30

75/100 x X + 3/4 x X + X x 1 = 30

0,75 x X + 0,75 x X + X x 1 = 30

X x ( 0,75 + 0,75 + 1 ) = 30

X x 2,5 = 30

X = 30 : 2,5 

X = 12