90 : xx = 6    

=> xx = 90 : 6 = 15

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

\(\Leftrightarrow\left(75\%+\frac{3}{4}+1\right)x=30\)

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

\(\Leftrightarrow x=30:\frac{5}{2}\)

\(\Leftrightarrow x=12\)

đổi 75%=3/4.Ta có:

3/4xX+3/4xX+X=30

(3/4+3/4+1)xX=30

    5/2     x    X=30

                 X  = 30:5/2

                X   = 12

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

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

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

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

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

\(x=12\)

giá xăng từ 20 000 đồng lên 21 000 đồng 1 lít . hỏi giá xăng tăng bao nhiêu phần trăm? 

40

Chúc bạn may mắn

(30% + 1) x X = 52

130% x X = 52

X = 52 : 130%

X = 40

0,75 x X + 0,75 x X + X = 30

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

X x 2,5 = 30

X = 30 : 2,5

X = 12

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

<=>3/4xX+3/4xX+X=30

<=>10/4xX=30

<=>10xX=120

<=>X=120/10=12

Vậy X=12

0,75x + 0,75x = 30

0,75 . 2x = 30

2x = 40

x = 20

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

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

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

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

\(x=12\)

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

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

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

\(\frac{3}{2}\cdot x+x=30\)

\(\frac{3}{2}\cdot x+\frac{1}{1}\cdot x=30\)

\(\left(\frac{3}{2}+\frac{1}{1}\right)\cdot x=30\)

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

\(x=30\text{ : }\frac{5}{2}\)

\(x=12\)

a)\(\Leftrightarrow\)\(x(27+30+43)=210500\)

\(\Leftrightarrow\)\(100x=210500\)

\(\Leftrightarrow\)\(x=2105\)

b)\(\Leftrightarrow\)\(x(128-12-16)=5208000\)

\(\Leftrightarrow\)\(100x=5208000\)

\(\Leftrightarrow\)\(x=52080\)

\(x\times27+x\times30+x\times43=210500\)

\(\Leftrightarrow x\times\left(27+30+43\right)=210500\)

\(\Leftrightarrow x\times100=210500\)

\(\Leftrightarrow x=2105\)

a: 27x+30x+43x=210500

nên 100x=210500

hay x=2105

b: 128x-12x-16x=5208000

nên 100x=5208000

hay x=52080

x+ \(\dfrac{30}{100}\)x=-1,3

x(1+\(\dfrac{30}{100}\))= -1,3

x. 1,3= -1,3

x = -1