VMO 1974 Problem 2

i) How many integers $n$ are there such that $n$ is divisible by $9$ and $n+1$ is divisible by $25$ ? ii) How many integers $n$ are there such that $n$ is divisible by $21$ and $n+1$ is divisible by $165$ ? iii) How many integers $n$ are there such that $n$ is divisible by $9, n + 1$ is divisible by $25$ , and $n + 2$ is divisible by $4$ ?