2581=2

I am not going to tell you why.
I will keep the secret with me.
Hint: 8888=8

I must have a low grade intelligence. ㅎ, ㅎ, ㅎ.

"저학력일수록 잘푼답니다.." was the key to the secret.
"저학력" means people with no knowledge of mathematics.
This means "not to see the numbers as numbers", or not to see it as a mathematic equation
which is the domain of highly educated.
You have to consider yourself as a "cave man" who never knew the symbols for numbers.
See the numbers here as pictures or signs (like a cave man), but not as numbers.

Just forget about the 4-digit numbers but see them as curved lines, straight lines, or circles.
Then consider the single digit numbers (after the equal sign) as counting numbers.
Then, you will know the answer.