Question
Predecessors of any given number can be simply calculated by subtracting 1 from the given number. So, the predecessor of any number $a$ is given by $\left( {a - 1} \right)$.
So, the predecessor of 10000 is $\left( {10000 - 1} \right) = 9999$ i.e., the predecessor of 10000 is 9999.