This is you homework, so I won't give you all the answers! Just the one to fix where you have tried to do it:
1) I would probably use a JOIN - you have to to return values from two or more tables - (and the name of a table and a field is wrong)
SELECT c.cus_name, m.mem_no FROM customer c
JOIN membership m ON m.cus_no = c.Cus_no
2) Again, you need a JOIN or more.
3) JOIN again, but this time with a WHERE clause looking at the cass_name column
4) Wrong syntax! JOIN again, but the COUNT syntax is "COUNT(*)" not "(*)COUNT"
Why not try it? You presumably have SQL server installed? Create your tables, populate your data and try your queries in Sql Server Management Studio!