Good question > 50% of the answer!

[deda]

Let the good question be your guide on the journey to the truth!
My question for you goes: Is the law of lever conditional law and if so then which condition is that?

[Antonio Lao]

If condition is to mean not absolute or mean having a solution.

There are physical equations that have infinite number of solution. A case in point are Einstein's field equations of general relativity.

others infinite solutions are the following:

At constant temperature, the product of initial pressure and volume is equal to the final pressure and volume.

P_i V_i = P_f V_f

Also for elastic collisions, the initial momentum is equal to the final momentum.

m_1 v^{i}_1 + m_2 v^{i}_2 = m_1 v^{f}_1 + m_2 v^{f}_2