これまでに提供されたものはどれも正しくないので、この答えを入れてください
select count(case when status = "accepted" then 1 end) /
count(case when status = "rejected" then 1 end) as Ratio
from my_table
where status in ("accepted","rejected")
個別のカウントも必要な場合
select count(case when status = "accepted" then 1 end) Accepted,
count(case when status = "rejected" then 1 end) Rejected,
count(case when status = "accepted" then 1 end) /
count(case when status = "rejected" then 1 end) as Ratio
from my_table
where status in ("accepted","rejected")
注:MySQLにはゼロ除算の問題はありません。 Rejectedが0の場合はNULLを返します。