6 is adding on the right, then it will subtract on the left
[tex]\begin{gathered} 8-6=\frac{a}{4} \\ 2=\frac{a}{4} \end{gathered}[/tex]4 is dividing on the right, then it will multiply on the left
[tex]\begin{gathered} 2\cdot4=a \\ 8=a \end{gathered}[/tex]