Explanation:
Reversible reactions that happen in a closed system eventually reach equilibrium. At equilibrium, the concentrations of reactants and products do not change. But the forward and reverse reactions have not stopped - they are still going on, and at the same rate as each other.
I believe this is a double replacement. As you can see none of the chemical symbols are missing, there just "replaced".
5 x 2 = 10
3 x 3 = 9
10/9, or 1 1/9 is your answer
hope this helps
