You hold Ace-4 — a soft 15, meaning the ace still counts as 11. Dealer shows 4. The correct basic-strategy play:
Against a weak dealer 4 (40% bust chance), soft 15 (Ace-4) is a doubling machine: you can't bust the draw, and every extra chip is placed while the dealer is in trouble. Double — if the table does not allow it, just hit.
Soft hands are where most casual players leak the most: they play them like hard totals and miss every profitable double. Learning the six soft-total rows of the chart is the fastest win-rate upgrade there is.