To find out how much money Samuel has in his bank account after withdrawing $39.78, you can subtract the amount he withdrew from the initial amount in his account.
Starting amount: $58.23
Withdrawn amount: $39.78
Now perform the subtraction:
\[ 58.23 - 39.78 = 18.45 \]
So, after the withdrawal, Samuel has $18.45 in his bank account.