Question: I came late to shul during the week and went to the ezras nashim to daven as no ladies come then. Was I included in the minyan?
Answer: The Shulchan Aruch (OC 55:13) writes that the 10 men who make up the minyan need to all be present in the same room as the chazzan. The Mishna Berura (55:48) writes that it doesn’t matter if they can’t all see each other providing that they are in the same room. While the Shulchan Aruch (OC 55:14) writes that one who is outside a shul can join in through an open window, the Mishna Berura (55:52) writes that they shouldn’t make up a minyan of people who are in two separate rooms divided by an open window, even if they can see each other (See Shaarei Teshuva; Shaar Hatziyun 55:53).
The Aruch Hashulchan (OC 55:20) writes that as the ezras nashim is separated by a proper mechitza, any men davening there can not join in as they are considered to be in a separate room, regardless as to whether they can see each other or not (See Kaf Hachaim OC 55:76).Thus, R’ Shmuel Wosner (Shevet Halevi 9:20:1) writes that while men learning there may respond amen, etc. as ladies would, they cannot be considered part of the minyan while there (See Halichos Shlomo, Tefilla 5:n18).