Anyone know any easy invention that s useful in the house or school?

what do you mean? like as in something you can invent?

For this you need paper and a writing utensil, any will do I use a pencil.
First you need to place a piece of paper on a table, then grab what ever writing utensil you have within your reach and place the pointy part on the paper. This lets you take notes and such I use it a lot.