We have the following equation
[tex]\begin{gathered} \frac{5}{6}=\frac{1}{3}+d \\ \end{gathered}[/tex]We substract 1/3 each side:
[tex]\begin{gathered} -\frac{1}{3}+\frac{5}{6}=-\frac{1}{3}+\frac{1}{3}+d \\ -\frac{1}{3}+\frac{5}{6}=0+d \\ -\frac{1}{3}+\frac{5}{6}=d \\ \end{gathered}[/tex]We multiply each side of the fraction 1/3 by 2:
[tex]-\frac{1}{3}=-\frac{1\cdot2}{3\cdot2}=-\frac{2}{6}[/tex]Then
[tex]\begin{gathered} -\frac{1}{3}+\frac{5}{6}=d \\ -\frac{2}{6}+\frac{5}{6}=d \\ \frac{3}{6}=\frac{1}{2}=d \end{gathered}[/tex]