Question

\(\frac{3-x}{12-x}\)=\(\frac{7}{3}\)

có mấy dấu gạch đó là lỗi đừng bận tâm

Answer 1

\(\frac{3-x}{12-x}=\frac{7}{3}\\ \Rightarrow3\left(3-x\right)=7\left(12-x\right)\\ \Rightarrow9-3x=84-7x\\ \Rightarrow9-84=-7x+3x\\ \Rightarrow-75=-4x\\ \Rightarrow x=-75:-4\\ \Rightarrow x=\frac{75}{4}=18.75\)

Answer 2

\(\frac{3-x}{12-x}=\frac{7}{3}\)

\(\Leftrightarrow\left(3-x\right).3=7.\left(12-x\right)\)

\(\Leftrightarrow9-3x=84-7x\)

\(\Leftrightarrow-3x+7x=84-9\)

\(\Leftrightarrow4x=75\)

\(\Leftrightarrow x=\frac{75}{4}\)