This seems like the basis of a good essay to me. When you say MIT has many opportunities, why don’t you say that in your essay, but explain what those opportunities are? I.e., I’ll continue my research at UROP using their __ and __,. And HOW is their math dept going to help you reach your goals? Write that.
I am not seeing that you are having great difficulty with this. If you show that MIT offers what you need and why you need to be there to do it, you will probably show what they are looking for in this type of essay.