Answer:
The first amount is larger by 25%.
Explanation:
To start, let's first increase a by 50% of a, or a/2. We will get 3a/2. Now, we decrease it by 50% of 3a/2, or just half 3a/2 to get 3a/4. This means the first amount is larger by (a - 3a/4)/a or (a/4)/a=1/4=25%.
Note: To increase a number by x%, we can just multiply it by (100+x)/100, and to decrease a number by x%, we can just multiply it by (100-x)/100.