Solve for a in the equation;
d = 2aN
In order to do that, we need to make a the subject of the equation and that means moving 2 and N to the other side, and making a isolated on one side of the equation. Start by dividing both sides of the equation by 2N and you have;
d/2N = 2aN/2N
d/2N = a
Therefore the solution for a is shown as
a = d/2N