In the table, the relation (x, y) is not a function if the missing value of x is

Ok I see. If the missing value of X is also 3, it would not be a function. A function can not have one x value with 2 y values. If you plot it and draw a line vertical through each point, you should only hit one point with each line. That is called the vertical line test. If i does not pass that test, it is not a function. The answer is 3

Iagree that is the answer to the question