Você pode usar uma subconsulta no
from
cláusula:select
s.invalidCount,
s.unknownCount,
s.totalCount,
invalidCount * 100 / s.totalCount as PercentageInvalid,
unknownCount * 100 / s.totalCount as PercentageUnknown
from
(select invalidCount = (SELECT COUNT(*) FROM <...a...> WHERE <...b...>),
unknownCount = (SELECT COUNT(*) FROM <...c...> WHERE <...d...>),
totalCount = (SELECT COUNT(*) FROM <...e...> WHERE <...f...>)) s