What is 400 times 400

The rumpart family is building a new room onto their house. the width of the new room will be 16 feet. the length of the room will be 4% greater than the width. write an expression to find the length of the new room. what will be the area of this new room?

Twice the sum of a number and 4 is equal to three times the difference of the number and 7. find the number.

4+(2+x) can you me solve this problem