Google Sheets sum only filtered

Question

I'm starting just to get familiar with excel and google docs, i have some previous experience with it, but obviously not enough to understand why in the world this function wouldn't work

=(SUBTOTAL(9,Augusti!E:E))/(SUBTOTAL(2,Augusti!E:E))

All I get is Error, Augusti is a reference to another page inside the same doc, the 9 stands for sum and the 2 stands for count correct me if I'm wrong, E:E contains a title row and the rest is just integers from 1 to 5.

All help is very much appreciated.

Regards

P.S.

while we're at it, is it possible to instead of typing Augusti and then september etc(A new page for each month) get the name from the column left of it to then use inside the above formula and get it evaluated correctly

Solved - Answer: Instead of comma , use semicolon ;

Answer 1

Solved - Answer: Instead of comma , use semicolon ;

The End Result ended up like this

=SUBTOTAL(101;INDIRECT(A2&"!D:D"))

It works in regular excel gets a little bugged up still in google docs sheets