Câu 1:15/35=3/7

216/270=4/5

250/750=1/3

Câu 2:8/18,12/27,16/36,20/45,24/54

Câu 3:1/2=2/4=3/6=4/8=5/10

Câu 4:2×3×5/2×7×5=30/70=3/7

Tk mình nhé bn!

Bài 1:

\(\frac{15}{35}=\frac{3}{7}\)

\(\frac{216}{270}=\frac{4}{5}\)

\(\frac{250}{750}=\frac{1}{3}\)

Bài 2:

5 phân số bằng phân số \(\frac{4}{9}\) là: \(\frac{8}{18};\frac{12}{27};\frac{16}{36};\frac{20}{45};\frac{24}{54}\)

Bài 3:

\(\frac{1}{2};\frac{2}{4};\frac{3}{6};\frac{4}{8};\frac{5}{10}\)

Bài 4:

\(\frac{2x3x5}{2x7x5}=\frac{3}{7}\)

\(1\)\(\frac{15}{35}\) \(=\)\(\frac{5}{7}\)

\(\frac{216}{270}\)= \(\frac{24}{30}\)

\(\frac{250}{750}\)\(=\)\(3\)

   \(2.\)\(\frac{8}{18}\); \(\frac{12}{27}\)   ; \(\frac{16}{36}\); \(\frac{20}{45}\); \(\frac{24}{54}\)

\(\frac{1}{2}\)=\(\frac{2}{4}\)= \(\frac{3}{6}\)=\(\frac{4}{8}\)=\(\frac{5}{10}\)

4.\(2\cdot3\cdot\frac{5}{2\cdot7\cdot5}\) = \(\frac{3}{7}\)

* \(20+65.4=\left(x+75\right):5+30\)

\(\Leftrightarrow20+260-30=\frac{x}{5}+\frac{75}{5}\)

\(\Leftrightarrow20+260-30-\frac{75}{5}=\frac{x}{5}\)

\(\Leftrightarrow235=\frac{x}{5}\Rightarrow x=235.5=1175\)

* \(2248:\left[119-\left(x-6\right)\right]=24\)

\(\Leftrightarrow2248:\left(119-x+6\right)=24\)

\(\Leftrightarrow2248:\left(125-x\right)=24\)

A mình lỡ tay, để mình tính tiếp nhá!

\(\Leftrightarrow125-x=2248:24\Leftrightarrow125-x=\frac{281}{3}\Rightarrow-x=\frac{94}{3}\Rightarrow x=-\frac{94}{3}\)(bài này mình thấy sai sai sao á, nếu mình làm sai thì thông cảm cho mình nhé!

* \(\left(x+70\right):14-40=\left(32.15\right):2\)

\(\Leftrightarrow\left(x+70\right):14=480:2+40\)

\(\Leftrightarrow\frac{x}{14}+5=280\Leftrightarrow\frac{x}{14}=275\Rightarrow x=3850\)

* \(x-4867=\left(175.2050.70\right):25+23\)

\(\Leftrightarrow x-4867-23=\left(175:25\right).\left(2050:25\right).\left(70:25\right)\)

\(\Leftrightarrow x-4890=7.82.\frac{14}{5}\)

\(\Leftrightarrow x-4890=\frac{8036}{5}\Rightarrow x=\frac{8036}{5}+4890=\frac{32486}{5}\)(bài này mình thấy hình như cũng có cái gì đó sai sai luôn hihi!)

=24 nha

(11/5+3/5x)=3/4

3/5x=3/4-11/5

x=29/20:3/5

x=29/12

2.5 x \(\frac{25}{x}\)=   \(\frac{5}{6}\)

\(\frac{62.5}{x}\)=\(\frac{5}{6}\)

\(x\)=      62.5     :      \(\frac{5}{6}\)

\(x\)=      62.5    x      \(\frac{6}{5}\)

\(x\)=      75

\(2.5\cdot\frac{25}{x}=\frac{5}{6}\)

\(=\frac{62.5}{x}=\frac{5}{6}\)

\(\Rightarrow62.5\cdot6=5x\)

375 = 5x

x = 375 : 5

x = 75

\(2,5\times\frac{25}{x}=\frac{5}{6}\)

\(\frac{25}{x}=\frac{5}{6}\div\frac{25}{10}\)

\(\frac{25}{x}=\frac{50}{150}\)

\(=>x=50\div25=2\)

\(=>\) \(150\div2=75\)

\(=>x=75\)

460 + 85 *4 = x + 175 / 5 + 30

460 + 340 = x + 35 + 30

800 = x + 65

x = 800 - 65

x = 735

 460 +  85 *4 = x + 175 :5 +  30    

    460 + 340  = x + 35 + 30

           800     = x + 65

            x         = 800 - 65 = 735

460+85*4=x+\(\frac{175}{5}\)+30

460+340=x+35+30

800=x+65

x=800-65=735

460 + 85 x 4 = x + 175/5 + 30

460 + 340 = x + 35 + 30

800 = x + 65

x = 800 - 65

x = 735

460 + 85 x 4 = x + 175/5 + 30

460 + 340 = x + 35 + 30

800 = x + 65

x = 800 - 65

x = 735

cảm ơn Hữu Nghĩa nhé , anh họ tôi