demo, Sql Server - rextester

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--Sql Server 2014 Express Edition
--Batches are separated by 'go'

WITH yourTable AS (
    SELECT 'Company A' AS Name, 'Sales' AS Item, 2017 AS Year, 100 AS Value UNION ALL
    SELECT 'Company A', 'Sales',  2016, 100 UNION ALL
    SELECT 'Company A', 'Sales',  2015, 400 UNION ALL
    SELECT 'Company A', 'Profit', 2017, 50 UNION ALL
    SELECT 'Company A', 'Profit', 2016, 50 UNION ALL
    SELECT 'Company A', 'Profit', 2015, 200 UNION ALL
    SELECT 'Company B', 'Sales',  2017, 200 UNION ALL
    SELECT 'Company B', 'Sales',  2016, 100 UNION ALL
    SELECT 'Company B', 'Profit', 2017, 20 UNION ALL
    SELECT 'Company B', 'Profit', 2016, 20
),

cte AS (
    SELECT
        Name,
        Year,
        100*MAX(CASE WHEN Item = 'Profit' THEN Value END) /
            MAX(CASE WHEN Item = 'Sales' THEN Value END) AS Margins
    FROM yourTable
    GROUP BY
        Name,
        Year
)

SELECT
    Name,
    Year,
    Margins,
    (Margins + LAG(Margins) OVER (PARTITION BY Name ORDER BY Year)) / 2 AS [2 yr Avg]
FROM cte
ORDER BY
    Name,
    Year;

View schema
Execution time: 0 sec, rows selected: 5, rows affected: 0, absolute service time: 0,14 sec