Given the series: $7, 8, 9, 7, 6, 5, 3, 4, 2, 8, 9, 7, 2, 4, 5, 9, 2, 9, 7, 6, 4, 7$. Which numbers have equal frequency?

$(I)$ Kamal is available at home from $12$ noon to $4$ $p.m.$ on Tuesday,Thursday,and Sunday.
$(II)$ His younger brother Navin is available at home on Monday,Thursday,Friday,and Sunday between $10$ $a.m.$ to $2$ $p.m.$
$(III)$ The eldest brother Rajiv is available between $9$ $a.m.$ to $12$ noon on Monday,Wednesday,and Thursday and $2$ $p.m.$ to $4$ $p.m.$ on Friday,Saturday,and Sunday.
On which day of the week are all three brothers available at home at the same time?

How many $7$'s are there in the following series which are preceded by $6$ but not preceded by $8$ (i.e.,the sequence $6, 7$ where $6$ is not immediately preceded by $8$)?
Series: $8, 7, 6, 7, 8, 6, 7, 5, 6, 7, 9, 7, 6, 1, 6, 7, 7, 6, 8, 8, 6, 9, 7, 6, 8, 7$

If $18^{th}$ February,$1997$ falls on Tuesday,then what will be the day on $18^{th}$ February,$1999$?

How many days will there be from $26^{th}$ January,$1988$ to $15^{th}$ May,$1988$ (both days included)?

In the following sequence of instructions,$1$ stands for Run,$2$ stands for Stop,$3$ stands for Go,$4$ stands for Sit and $5$ stands for Wait. If the sequence were continued,which instruction will come next?
$4, 4, 5, 4, 5, 3, 4, 5, 3, 1, 4, 5, 3, 1, 2, 4, 5, 4, 5, 3, 4, 5, 3$