Dear Aspirant

Hope you are doing well

Now let me go through your question

Let H be the set of people who speak Hindi, and E be the set of people who speak English

∴n(H∪E)=400,n(H)=250,n(E)=200

n(H∩E)=?

We know that:

n(H∪E)=n(H)+n(E)−n(H∩E)

∴400=250+200−n(H∩E)

⇒400=450−n(H∩E)

⇒n(H∩E)=450−400

∴n(H∩E)=50

It is more easy if you  make its venn diagram