First let's get rid of the [tex]d^2[/tex] in the denominator of the fraction on the right side of the equation. This will help to get only [tex]x[/tex] and a coefficient on one side of the equation:
[tex]A = \dfrac{730x}{d^2}[/tex]
[tex]d^2A = 730x[/tex]
Now, simply divide by 730 to find [tex]x[/tex]:
[tex]d^2A = 730x[/tex]
[tex]\boxed{\dfrac{d^2A}{730} = x}[/tex]