Which is correct

Were you too stupid to grasp it?

Were you to stupid to grasp it?

Were you too stupid to grasp it?

Explanation:

To is a preposition with several meanings, including “toward” and “until.” Too is an adverb that can mean “excessively” or “also.” like "I want to go too!" Just to be clear: two is pronounced the same as to and too, but it can't be used instead of either of them because it's a number.