\(a,\dfrac{x}{7}=\dfrac{6}{21}\Rightarrow x.21=7.6=42\\ \Rightarrow x=2\\ b,\dfrac{1}{2}=\dfrac{x}{12}\Rightarrow1.12=2.x=12\\ \Rightarrow x=6\\ c,\dfrac{-7}{6}=\dfrac{x}{12}\Rightarrow-7.12=6.x=-84\\ \Rightarrow x=-14\)
a, \(\dfrac{x}{7}=\dfrac{6}{21}\Rightarrow3x=6\Leftrightarrow x=2\)
b, \(\dfrac{1}{2}=\dfrac{x}{12}\Rightarrow x=6\)
c, \(-\dfrac{7}{6}=\dfrac{x}{12}\Rightarrow x=-14\)
d, thiếu đề
câu a,x/7=6/21=>21x=6.7=>21x=42=>x=2
câu b,1/2=x/12=>12=2x=>x=6
câu c,-7/6=x/12=>-7.12=6x=>x=-14
câu d,-x/7=6/y=>-xy=6.7=42.thay y bằng bn vào r tính
