Query Error when trying to run query
You have to join the tables on a value.  I'm taking a wild guess here, but I think you might be looking for something like this:

SELECT (SELECT CONCAT(ROUND(SUM(server.Tech=7)/COUNT(server.Tech) * 100,2), '%') AS Server,
CONCAT(ROUND(SUM(network.Tech=7)/COUNT(network.Tech) * 100,2), '%') AS Network
           FROM network join server

On network.Tech = server.Tech

) AS V,


I don't know what your equals sign is doing in your arithmetic operation.  Are you trying to pull all Tech where it equals 7?  If so, it would be

SELECT (SELECT CONCAT(ROUND(SUM(server.Tech)/COUNT(server.Tech) * 100,2), '%') AS Server,
CONCAT(ROUND(SUM(network.Tech)/COUNT(network.Tech) * 100,2), '%') AS Network
           FROM network join server

On network.Tech = server.Tech
WHERE server.Tech = 7 AND network.Tech=7

) AS V,


Of course, if you are trying to sum all Techs that equal 7 over the full rowcount, it will need more work.