\(\frac{72-x}{3}=\frac{x-18}{5}\)

\(\Rightarrow\frac{\left(72-x\right).5}{15}=\frac{3\left(x-18\right)}{15}\)

\(\Rightarrow\left(72-x\right).5=3\left(x-18\right)\)

\(\Rightarrow360-5x=3x-54\)

\(\Rightarrow-3x-5x=-360-54\)

\(\Rightarrow-8x=-414\)

\(\Rightarrow x=51,75\)

+) Vì \(\frac{72-x}{3}=\frac{x-18}{5}\)

\(\Rightarrow5\left(72-x\right)=3\left(x-18\right)\)

     \(5.72-5x=3x-3.18\)

      \(360-5x=3x-54\)

       \(-5x-3x=-54-360\)

       \(-8x=-414\)

              \(x=-414:\left(-8\right)\)

              \(x=51,75\)

      Vậy x = 51,75

\(\frac{72-x}{3}=\frac{x-18}{5}\)

\(\Leftrightarrow5\left(7x-2\right)=3\left(x-18\right)\)

\(\Leftrightarrow360-5x=3x-54\)

\(\Leftrightarrow360=3x-54+5x\)

\(\Leftrightarrow360=8x-54\)

\(\Leftrightarrow8x-54=360\) (chuyển vế)

\(\Leftrightarrow8x=360+54\)

\(\Leftrightarrow8x=414\)

\(\Leftrightarrow x=\frac{414}{8}=\frac{207}{4}\)

\(\Rightarrow x=\frac{207}{4}\)

\(\frac{72-x}{3}=\frac{x-18}{5}\)

<=> 360 - 5x = 3x - 54

<=> -8x = -414

<=> x = \(\frac{207}{4}\)

5(72-x)=3(x-18)

360 - 5x = 54 - 3x

-5x +3x = 54-360

-2x        =  -306

  x = -306 : -2 = 153

\(\frac{72-x}{3}=\frac{x-18}{5}\)

\(\frac{5\left(72-x\right)}{3.5}=\frac{3\left(x-18\right)}{5.3}\)

\(\frac{360-5x}{15}=\frac{3x-54}{15}\)

\(\Rightarrow360-5x=3x-54\)

\(\Rightarrow360+54=3x+5x\)

\(\Rightarrow414=8x\)

\(\Rightarrow x=\frac{414}{8}=\frac{212}{4}=\frac{106}{2}=\frac{53}{1}=53\)

\(\Rightarrow x=53\)