\(y=12-\left(\dfrac{1}{3}\times4\right)=12-\dfrac{4}{3}=\dfrac{32}{3}\)

\(y=\left(\dfrac{12}{35}\times\dfrac{14}{9}\right)-\dfrac{2}{5}=\dfrac{8}{15}-\dfrac{2}{5}=\dfrac{2}{15}\)

a) \(y+\dfrac{1}{3}\times4=12\)

\(y+\dfrac{1}{3}=12:4\)

\(y+\dfrac{1}{3}=3\)

\(y=3-\dfrac{1}{3}\)

\(y=\dfrac{8}{3}\)

b) \(\dfrac{2}{5}+y=\dfrac{12}{35}\times\dfrac{14}{9}\)

    \(\dfrac{2}{5}+y=\dfrac{8}{15}\)

           \(y=\dfrac{8}{15}-\dfrac{2}{5}\)

          \(y=\dfrac{2}{15}\)

2/15

\(\dfrac{19}{28}+\dfrac{23}{47}-\dfrac{15}{8}+\dfrac{9}{28}+\dfrac{24}{47}\)

\(=\left(\dfrac{19}{28}+\dfrac{9}{28}\right)+\left(\dfrac{23}{47}+\dfrac{24}{47}\right)-\dfrac{15}{8}\)

\(=\dfrac{28}{28}+\dfrac{47}{47}-\dfrac{15}{8}\)

\(=1+1-\dfrac{15}{8}\)

\(=\dfrac{1}{8}\)

____________________

\(\dfrac{30}{11}+\dfrac{12}{35}-\dfrac{19}{11}-\dfrac{2}{35}-\dfrac{2}{7}\)

\(=\left(\dfrac{30}{11}-\dfrac{19}{11}\right)+\left(\dfrac{12}{35}-\dfrac{2}{35}\right)-\dfrac{2}{7}\)

\(=\dfrac{11}{11}+\dfrac{10}{35}-\dfrac{2}{7}\)

\(=1+\dfrac{2}{7}-\dfrac{2}{7}\)

\(=1\)

\(35.\left(x-4\right)^2=875\)

\(\Leftrightarrow\left(x-4\right)^2=25\)

\(\Leftrightarrow\orbr{\begin{cases}x-4=-5\\x-4=5\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=-1\\x=9\end{cases}}\)

Vậy \(x=-1\)hoặc \(x=9\)

\(35.\left(x-4\right)^2=875\)

\(< =>\left(x-4\right)^2=\frac{875}{35}=25\)

\(< =>\orbr{\begin{cases}x-4=5\\x-4=-5\end{cases}< =>\orbr{\begin{cases}x=9\\x=-1\end{cases}}}\)

35( x - 4 )² = 875

<=> ( x - 4 )² = 25

<=> ( x - 4 )² = ( ±5 )²

<=> x - 4 = 5 hoặc x - 4 = -5

<=> x = 9 hoặc x = -1

\(y\times7=5,6\%\)

\(\Leftrightarrow y\times7=\dfrac{5,6}{100}\)

\(\Leftrightarrow y=\dfrac{5,6}{100}:7=\dfrac{1}{125}\)

1/125

1/125

Y x 100 = 388600

Y = 3886

y×100=388600

y=388600÷100

y=3886

Y x 100 = 388 600

Y           = 388 600 ：100

Y           = 3886

a: =>16/x=-4/5

hay x=-20

b: =>x+7/15=-2/3

=>x+7=-10

hay x=-17