Answer
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
There is nothing wrong if a mosque’s imam teaches men and women without a barrier.
Answering your question about if a mosque’s imam can teach women with no barrier, Dr. Jasser Auda, Professor and Al-Shatibi Chair of Maqasid Studies at the International Peace College South Africa, states:
Yes, a mosque’s imam can teach men and women without a barrier. This is the Sunnah of Prophet Muhammad (peace be upon him). That is how he conducted his lessons in his mosque.
The Prophet’s mosque did not have any barriers. It also did not have any floors or balconies for men and women. Men and women were in one space where men made rows in the front and behind them were the women’s rows. This is the sunnah of Prophet Muhammad (peace be upon him)
You mentioned in your question the term ‘non-Muslim country‘. Really countries are not Muslim or non-Muslim. A country where you are allowed to have mosques, give adhan, pray and practise the Islamic rituals is an Islamic land. And in that sense is the land where Muslims could live.
Whether the majority 51% is Muslim or not is a political question and has nothing to with the rules that govern the Muslims’ behavior and the mosques and what Muslims do. The rules are the same whether Muslims are a majority or a minority.
Almighty Allah knows best.