Find their similarities and differences and then put that into words.
Without the comparative it means:
"The tiger is __ stupid than the donkey".
'Burro' itself can also be used an insult to call someone stupid, so I think it'd be "El tigre es menos tonto que el burro."
I want to say 'la cuchara'
Hope que te ayude!!
It’s easy just usetranslate and write in English to get the translated answer. Comment if u have any more questions