How to get from Holiday inn express mongkok to Hong Kong airport?

You can take bus no.A21 at Changsha Street, Nathan Road and go to the airport directly. The travel time is about 55 mins. The ticket fare is 33 HKD per person.

Thanks.
I will be fly to HK Stay 1 day at Macau. From HK airport can I transfer to Macau ferry? In term of value added, Which public transport card should I take?

Of course. After landing at HKIA, no need to go through the immigration. Directly walk to the ferry ticket counter to get a ticket and show ur luggage tag receipt (the staff will handle the baggage for you). Then take free shuttle bus to Skypier to check your luggage and board the ferry. And personally, it is no need to have a transport card in Macau, because buses are cheap and there are many free shuttle buses for choices.

Thanks. You mean HKIA Terminal 2 also can directly walk to the ferry ticket counter?

Yeah. Actually, the tickets can be bought at the Ticketing Counter at Transfer Area E2, Arrivals Level, T1. From T2, you need walk or take the subway to T1 and walk to the ticket counter.