Just try this:
SELECT
l.LoanNumber,
l.LoanDeterminationScore 'FICO',
CAST(FLOOR (l.LoanDeterminationScore / 20) * 20 AS VARCHAR(10)) + '-' +
CAST(FLOOR (l.loanDeterminationScore / 20) * 20 + 19 AS VARCHAR(10)) AS 'Range'
FROM
loan.LoanQA l
WHERE
l.FundedDate = '10/15/2013'
Just CAST
the numeric values to a string type, concatenate with +
, and you're done!