In order to find the value of N, you just have to simplify the equation and apply some properties of equality.
Let's start solving this;
0.00102 = 102/N
Apply Multiplication Property of Equality which is to multiply both sides of the equation with N
N(0.00102) = (102/N)(N)
0.00102N = 102
Next is to multiply both sides of the equation with (1/0.00102)
(1/0.00102)(0.00102N) = (102)(1/0.00102)
N = 100,000
We are already done solving for N.
Therefore, the value of N is 100,000