Question

VD 8:Tìm x biết :

a,\(\dfrac{x}{3}\) + \(\dfrac{x}{4}\) =\(\dfrac{7}{4}\)

Answer 1

a, \(\dfrac{x}{3}+\dfrac{x}{4}=\dfrac{7}{4}\)

\(\Rightarrow x\cdot\left(\dfrac{1}{3}+\dfrac{1}{4}\right)=\dfrac{7}{4}\)

\(\Rightarrow x\cdot\dfrac{7}{12}=\dfrac{7}{4}\)

\(\Rightarrow x=\dfrac{7}{4}:\dfrac{7}{12}\)

\(\Rightarrow x=3\)

Answer 2

\(\dfrac{x}{3}+\dfrac{x}{4}=\dfrac{7}{4}\)

\(\Rightarrow\dfrac{4x}{12}+\dfrac{3x}{12}=\dfrac{7}{4}\)

\(\Rightarrow\dfrac{4x+3x}{12}=\dfrac{7}{4}\)

\(\Rightarrow\dfrac{7x}{12}=\dfrac{7}{4}\)

\(\Rightarrow\left(7x\right).4=12.7\)

\(\Rightarrow\left(7x\right).4=84\)

\(\Rightarrow7x=21\)

\(\Rightarrow x=3\)

vậy x=3