Final answer:
To find the cost of the flooring, you need to multiply the area of the room by the cost per square foot.
Step-by-step explanation:
The area of the square dining room can be found by squaring the length of one side. In this case, the length of one side is x feet, so the area of the room is x * x = x^2 square feet.
The cost of the flooring is determined by multiplying the area of the room by the cost per square foot. The cost per square foot is $3.50. So, the cost of the flooring is 3.5 * x^2 dollars.