Using ratios for this is not the best way, it would be better to represent time between attacks as a function of attacks per second i.e.

Let n = number of attacks per second, and let t = the time between each attack:
We can surmise that if you have n attacks per second, and t time between each attack, then t*n = 1 second.

We can then use what you said about operating on an equation. Because we’re trying to find t, we would divide both sides by n. t*n÷n = n, and 1÷n = 1/n, so t = 1/n