In order to solve the formula
[tex]C=\pi d[/tex]
in terms of d, you simply have to divide both sides by pi:
[tex]d=\dfrac{C}{\pi}[/tex]
The total height of the earring is the sum of the diameters of the circles. Given their circumferences, the diameters are
[tex]d_1=\dfrac{6}{\pi},\quad d_2=\dfrac{8}{\pi}[/tex]
So, the total height is
[tex]h=d_1+d_2=\dfrac{6}{\pi}+\dfrac{8}{\pi}=\dfrac{14}{\pi}[/tex]
