Assuming a structure, at its simplest, as:

CREATE TABLE table1 (id INT, a INT)

CREATE TABLE table2 (id INT, b INT)

INSERT INTO table1

SELECT 1,1 UNION SELECT 2,2 UNION SELECT 3,3

INSERT INTO table2

SELECT 1,1 UNION SELECT 2,2 UNION SELECT 3,3

Then:

CREATE TABLE table3 (id INT IDENTITY(1,1), e INT, f INT,

divided AS ((e/f) * CAST(1 AS DECIMAL(10,2)) ) )

INSERT INTO table3 (e, f)

SELECT (SUM(t1.a) / COUNT(t1.id)) [e],

(SUM(t2.b) / COUNT(t2.id)) [f]

FROM table1 t1, table2 t2

The 'divided' column in table3 will be your result. You can use temporary tables instead of permanent ones for simplicity.

Tested OK.