Question

look at this table:
x | y
12 | 4
5 | 18
16 | 8
5 | 4
5 | -8
is this relation a function?
yes no

Explanation:

A relation is a function if every input (x-value) has exactly one output (y-value). Here, the x-value 5 maps to three different y-values: 18, 4, and -8, violating the function definition.

Answer:

no