@miladreaamy From the top-right and bottom-left pictures, we can see that two Ashes are 10 kg heavier than two Pikachus. Therefore, one Ash is 5 kg heavier than one Pikachu.
From the top-left picture, we know that one Ash weighs 25 kg, so one Pikachu weighs 20 kg.
The answer is 20 kg.