Part A: From the diagram of the room, it is clear that the width is w=x+4.
Let l be the length of the room so it follows:

Hence the expression for the total area of the room if the area is A is given by:

Part B: It is given that the length is 12 units so l=12, therefore it follows:

So the area from part A at x=10/3 will be:

Hence the total area of both rooms is 88 square feet.