Answer:
The following numbers ARE functions:
2, 3, 6, 7, 9, 12
Explanation:
A function is only possible if the x values have NO REPEATING NUMBER!!!
Every number that isn't mentioned above has at least 1 number in it's x-values that repeats.
Question 1 has the 8 and 4 with 2 numbers.
Question 4 the 3 repeating. (There are 2 dots over the 3)
Question 5 has numbers 1 and 5 repeating many times
Question 8 numbers 1 and 2 are repeated twice
Question 10 number 3 repeats twice
Question 11 has the 1 repeated