sau các phép tính đó thì tổng bao nhiêu vậy bạn ? hình như đề hơi sai

=>y+y*1,5+y*3,5=225

=>6y=225

=>y=37,5

y + y x 4,5 : 3 + y x 7 : 2 = 255

y + y x 1,5 + y x 3,5 = 255

3y x (1,5 + 3,5) = 255

3y x 5 = 255

3y = 255 : 5

3y = 51

y = 51 : 3

y = 17

\(y+y+\dfrac{1}{4}\times\dfrac{7}{2}+y+\dfrac{1}{8}=139\)

\(3\times y+\dfrac{7}{8}+\dfrac{1}{8}=139\)

\(3\times y+1=139\)

\(3\times y=138\)

\(y=46\)

Vậy y = 46.

\(\dfrac{2}{5}\) x y : \(\dfrac{7}{4}\) = \(\dfrac{7}{8}\)

\(\dfrac{2}{5}\) x y = \(\dfrac{7}{8}\) x \(\dfrac{7}{4}\)

 \(\dfrac{2}{5}\) x y = \(\dfrac{49}{32}\)

         y = \(\dfrac{49}{32}\) : \(\dfrac{2}{5}\)

         y = \(\dfrac{245}{64}\)

2\(\dfrac{2}{5}\): y x 1\(\dfrac{1}{4}\) = 2\(\dfrac{3}{5}\)

\(\dfrac{12}{5}\): y x \(\dfrac{5}{4}\) = \(\dfrac{13}{5}\)

\(\dfrac{12}{5}\): y        = \(\dfrac{13}{5}\): \(\dfrac{5}{4}\)

 \(\dfrac{12}{5}\): y = \(\dfrac{52}{25}\)

        y = \(\dfrac{12}{5}\): \(\dfrac{52}{25}\)

        y = \(\dfrac{15}{13}\)

`y+7/2xxy+yxx3/5=102`

`y+7/2xxyxx1xx+yxx3/5=102`

`yxx(7/2+1+3/5)=102`

`yxx5,1=102`

`y=102:5,1`

`y=20`

Vậy..

`@An`

Ta có : \(\frac{x}{4}=\frac{y}{7}\) 

\(\Rightarrow\frac{x^2}{16}=\frac{y^2}{49}=\frac{3x^2}{48}=\frac{4y^2}{196}=\frac{3x^2-4y^2}{48-196}=\frac{100}{-148}=-\frac{25}{37}\)

Thay vào là ra nhé !:D

Cái chỗ Nguyễn Quang Trung đúng ròi

\(\Rightarrow\hept{\begin{cases}\frac{x}{4}=-\frac{25}{37}\\\frac{y}{7}=-\frac{25}{37}\end{cases}}\Rightarrow\hept{\begin{cases}x=-\frac{100}{37}\\y=-\frac{175}{37}\end{cases}}\)

CHTT nha bạn !