20 is the lowest of the upper 3 numbers, so the missing number must be 19 when averaged with 20. That is, the missing number must be ...
2*19 -20 = 18
Answer:
No, because <em>x</em> has multiple values for <em>y</em>.
Step-by-step explanation:
Any input into a function has to map into exactly one output. The input, <em>x</em>, has multiple values for <em>y</em>. Therefore, it is not a function.