\(\frac{x}{12}=\frac{5}{4}\)l

\(\Rightarrow x=\frac{5.12}{4}\)

\(\Rightarrow x=15\)

\(\frac{-8}{x}=\frac{16}{6}\)

\(\Rightarrow x=\frac{-8.6}{16}\)

\(\Rightarrow x=-3\)

làm giúp mình 2 bài cuối nha bạn tks trước

(0,5x-3)/4x=3/16

=>16×(0,5x-3)=4x×3

=>8x-48=12x=>8x-12x=48

=>-4x=48=>x=-12

\(0,5x-\frac{3}{4}x=\frac{3}{16}\)

\(\frac{1}{2}x-\frac{3}{4}x=\frac{3}{16}\)

 \(\left(\frac{1}{2}-\frac{3}{4}\right)x=\frac{3}{16}\)

\(\frac{-1}{4}x=\frac{3}{16}\)

         \(x=\frac{3}{16}:\left(\frac{-1}{4}\right)\)

         \(x=-\frac{3}{4}\)

Vậy.........................

a) 12/16 = -x/4    <=> 12.4=-x.16   <=> -16x=48    <=> x= -48/16=-3

12/16=21/y    <=> 12.y=16.21    <=>12y=336     <=> y= 336:12    <=> y=28

b)   3/x =-42/70    <=>   -42.x=70.3      <=>  -42x=210    <=> x=210/(-42)=-5

y/35=-42/70   <=> 70.y=-42.35       <=>70y=-1470     <=>  y= -1470: 70=-21

a) x = -3 ; y = -11 hoặc x = 3 ; y = 11

b) x = 10 ; y = 6  

c) 

\(\frac{x}{20}=\frac{3}{4}\)

\(\Rightarrow x\times4=20\times3\)

\(\Rightarrow x=\frac{20\times3}{4}\)

\(\Rightarrow x=15\)

\(b,\frac{4}{x}=\frac{x}{16}\)

\(\Rightarrow x\times x=4\times16\)

\(\Rightarrow x^2=64\)

\(\Rightarrow x=8\)

c , Không hiểu đề bài

\(\frac{x}{20}\)=\(\frac{3}{4}\)khi x=15

\(\frac{4}{x}\)=\(\frac{x}{16}\)khi x²=64 khi x =8

\(\frac{3}{x}\)=\(\frac{9}{-5}\)khi 9x= -15 khi x=\(\frac{5}{3}\)