Answer. Equilibrium state is attainable from either way means that it is attainable either you start the reaction by taking reactants or start the reaction by taking products. In reversible reactions not only reactants react to form products but products also react or decompose to form the reactants. In case of reaction between hydrogen and iodine to form hydrogen iodide, equilibrium state is attainable either you state the reaction by taking hydrogen and iodine, such as:
H2 (g) + I2(g) 2HI(g)
In this case purple colour of iodine disappears as it reacts to form colorless hydrogen iodine.
Or you start the reaction by taking hydrogen iodide, such as:
2HI (g) H2(g) + I2(g)
In this case purple colour of iodine disappears as it is formed from hydrogen iodide.
As this is reversible reaction, equilibrium state will be attained and reaction will be represented, as:
H2(g) + I2(g) <===> 2HI(g)
Showing establishment of reversible reaction