Let's say the number of fish that was in the tank before was x

If you caught 4 fewer fish than the number that was there, then you caught x-4

After adding x-4 fish into the tank, the tank now had 20 fish, meaning the total number of fish in the tank is x+x-4=20

2x=20+4

The total number of fish that was initially in the tank is 2x=24

Initially, there were x=24/2 fish in the tank

x=<<12=12>>12

If you caught 4 fewer fish than the number in my tank initially, you caught 12-4=<<12-4=8>>8 fish.

# Answer

8
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
I caught 4 fewer fish than the number in my tank and added them to my fish tank. If the tank has 20 fish right now, how many did I add?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
8
I caught 4 fewer fish than the number in my tank and added them to my fish tank. If the tank has 20 fish right now, how many did I add?
train