[tex]\bf \begin{array}{ccll} \stackrel{tablespoons}{salt}&\stackrel{cups}{flour}\\ \cline{1-2} \frac{2}{3}&\frac{3}{4}\\\\ x&3 \end{array}\implies \cfrac{~~\frac{2}{3}~~}{x}=\cfrac{~~\frac{3}{4}~~}{3}\implies \cfrac{~~\frac{2}{3}~~}{\frac{x}{1}}=\cfrac{~~\frac{3}{4}~~}{\frac{3}{1}}[/tex]
[tex]\bf \cfrac{2}{3}\cdot \cfrac{1}{x}=\cfrac{~~\begin{matrix} 3 \\[-0.7em]\cline{1-1}\\[-5pt]\end{matrix}~~}{4}\cdot \cfrac{1}{~~\begin{matrix} 3 \\[-0.7em]\cline{1-1}\\[-5pt]\end{matrix}~~}\implies \cfrac{2}{3x}=\cfrac{1}{4}\implies 8=3x\implies \cfrac{8}{3}=x\implies 2\frac{2}{3}=x[/tex]