Place it at the reveal in a maths or quiz edit, after the question is shown and just before the answer is confirmed on screen. Follow it with a correct answer sting, then a funny laugh to keep the classroom joke light and give the next scene room to start.
About this sound
This is a short Portuguese voice clip, just under six seconds, in which a speaker works through 20+20+20+7 and announces the answer, 67, to the teacher. The delivery is bright, confident and a little cheeky, as if the sum was never in doubt. It feels playful and triumphant, the sound of someone proudly getting the easy question right.