The Hong Kong Dollar (HKD) is pegged to the US Dollar at 1 USD = 7.75–7.85 HKD (narrow band).
At the typical mid-rate of 7.80:
HKD 20 ≈ USD 2.56
Rates fluctuate slightly daily. For real-time conversion, use a currency converter (XE, OANDA, Google) or check with your bank/exchange service.