x=4/5

新春的3很很踩才吧?

\(7,5x:\left(9-\frac{139}{21}\right)=\frac{63}{25}\)

\(7,5x:\left(\frac{189}{21}-\frac{139}{21}\right)=\frac{63}{25}\)

\(7,5x:\left(\frac{50}{21}\right)=\frac{63}{25}\)

\(7,5x=\frac{63}{25}.\frac{50}{21}\)

\(7,5x=6\)

\(x=6:7,5\)

\(x=\frac{4}{5}\)

vậy \(x=\frac{4}{5}\)

k mk nha vì mk đang âm điểm 

Giải:

\(7,5x:\left(9-6\dfrac{13}{21}\right)=2\dfrac{13}{25}\)

\(\Leftrightarrow7,5x:\left(9-\dfrac{139}{21}\right)=\dfrac{43}{25}\)

\(\Leftrightarrow7,5x:\dfrac{50}{21}=\dfrac{43}{25}\)

\(\Leftrightarrow7,5x=\dfrac{43}{25}.\dfrac{50}{21}\)

\(\Leftrightarrow7,5x=\dfrac{86}{21}\)

\(\Leftrightarrow x=\dfrac{86}{21}:7,5\)

\(\Leftrightarrow x=\dfrac{172}{315}\)

Vậy ...

\(7,5x:\left[9-6\frac{13}{21}\right]=2\frac{13}{25}\)

\(\Leftrightarrow7,5x:\left[9-\frac{139}{21}\right]=\frac{63}{25}\)

\(\Leftrightarrow7,5x:\frac{50}{21}=\frac{63}{25}\)

\(\Leftrightarrow7,5x=\frac{63}{25}.\frac{50}{21}\)

\(\Leftrightarrow7,5x=6\)

\(\Leftrightarrow x=6:7,5\)

\(\Leftrightarrow x=\frac{4}{5}=0,8\)

(Chúc bạn học tốt và tíck cho mìk vs nha!)

7,5x:\(\frac{50}{21}\)=\(\frac{64}{25}\)

7,5x = \(\frac{64}{25}.\frac{50}{21}\)

7,5x = \(\frac{128}{21}\)

x = \(\frac{128}{21}:7,5\)

x = \(\frac{256}{315}\)

256

315

Đáp án: 256/315

a) \(\dfrac{7}{5}x\div\left(9-6\dfrac{13}{21}\right)=2\dfrac{13}{25}\)

\(\dfrac{7}{5}x\div\left(9-\dfrac{139}{21}\right)=\dfrac{63}{25}\)

\(\dfrac{7}{5}x\div\dfrac{50}{21}=\dfrac{63}{25}\)

\(\dfrac{7}{5}x=6\)

\(x=\dfrac{30}{7}\)

b) \(\left(1,16-x\right)\times5,25\div\left(10\dfrac{5}{9}-7\dfrac{1}{4}\right)\times2\dfrac{2}{17}=75\%\)

\(\left(1,16-x\right)\times5,25\div\left(\dfrac{95}{9}-\dfrac{29}{4}\right)\times\dfrac{36}{17}=\dfrac{75}{100}\)

\(\left(1,16-x\right)\times5,25\div\dfrac{119}{36}=\dfrac{17}{48}\)

\(\left(1,16-x\right)\times5,25=\dfrac{2023}{1728}\)

\(1,16-x=\dfrac{289}{1296}\)

\(x=0,9370061728\)

52 ×.(y : 78) = 3380

         y : 78   = 3380 : 52

         y : 78   = 65

         y           = 65 ×. 78

         y           = 5070