What goes in the place of the “?” I don’t know how to do this

In a school 2/3 of the students study a language of those who study a language 2/5 study french

Isaac wants the equation below to have no solution when the missing number is placed in the box. which number should he place in the box?

Hey everyone! this question is a challenge question. for 50 points if you wish. all you have to do is answer the correct it has to be correct, in under 50 seconds, and i will make you the ! you want to accept this challenge. i already know! i mean, it's 50 free points! here is the question: 11x2= answer this correct, you get two prizes. don't forget. you only have 50 seconds or it wont happen. get it correct in under 50 seconds! that's not bad. so stop reading this long thing and !