There are three ways to avoid the "Division by zero encountered" error in your SELECT statement and these are as follows:
SELECT CASE WHEN [Denominator] = 0 THEN 0 ELSE [Numerator] / [Denominator] END AS [Percentage]
FROM [Table1]
SELECT ISNULL([Numerator] / NULLIF([Denominator], 0), 0) AS [Percentage]
FROM [Table1]
SET ARITHABORT OFF
SET ANSI_WARNINGS OFF
SELECT [Numerator] / [Denominator]
SET ARITHABORT OFF
SET ANSI_WARNINGS OFF
SELECT ISNULL([Numerator] / [Denominator], 0)