Tsumego (Capture) #5309478 (2-move)
Black to play — capture the marked white stones
Capture these stones
Why this move works
The answer is B5 then A6. The three white stones (A7, B7, B6) have liberties at A6 and B5.
Play B5 first. If you fill A6 first, White extends to B5. Close the escape at B5, then fill A6 to capture.