Explanation

Let's say Asad gives x sweets to Ahsan.

Then, Asad will have 20 - x sweets left.

And Ahsan will have 55 + x sweets.

We want Ahsan to have four times as many sweets as Asad, so we set up the equation:

55 + x = 4(20 - x)

Simplifying the equation, we get:

55 + x = 80 - 4x

Add 4x to both sides:

55 + 5x = 80

Subtract 55 from both sides:

5x = 25

Divide by 5:

x = 5

So Asad should give 5 sweets to Ahsan.

Then, Asad will have 20 - 5 = 15 sweets.

And Ahsan will have 55 + 5 = 60 sweets.

Indeed, Ahsan will have four times as many sweets as Asad: 60 = 4 × 15.

The correct answer is: 5