You hold Ace-7 — a soft 18, meaning the ace still counts as 11. Dealer shows 6. The correct basic-strategy play:
Against a weak dealer 6 (42% bust chance), soft 18 (Ace-7) 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, stand on your 18.
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.