Life In 19x19

Thanks! Either I missed 2, or it didn't register as life somehow

And thanks for the welcome

I am confused by the following problem given in Graded Problems for Beginners (problem 219 on p45)...

$$B
$$ --------------
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . . X . X X X
$$ | . . . X 2 O O
$$ | . . X O 4 O .
$$ | . . X O 3 5 1
$$ | . . . X O O O
$$ | . . . X X X ...