It is important to understand the words of the problem for solving this question.
Number of baseball games Bernie won last year = 24
Percentage of less games that Bernie won this year = 25%
Then
Number of games won less by Bernie this year = (25/100) * 24
= (1/4) * 24
= 6
So it can be seen that Bernie won 6 less games this year.
Now
The total number of games won by Bernie this year = 24 - 6
= 18
So Bernie won a total of 18 games this year. I hope the procedure is clear to you and the answer deduced is actually the one you were looking for.