Can you Explain this?

[choppe]

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[Ayeshlive]

The red block has a (horizontal) width of 8 units, and the green one has 5.
So, you can shift the yellow block 3 units left and put the green one left to it so you get 4 "hole" cells.
Then, shift the yellow one 1 unit down and then you can neatly stack the red one on it.
green block was 2 units tall earlier, and the red one is now 3 units tall. But as we shifted the yellow one 1 unit down, final result is same.

 

[tnnera]

bumpioooo

 

[chathupatiya]