Answer:
y = 8x
Explanation:
You want the proportional relationship indicated by the values in the table: (x, y) ∈ {(0.5, 4), (1, 8), (1.5, 12), (2, 16)}.
Proportional relation
The answer box tells you the relation can be described by the equation ...
y = kx
where k is some constant.
It is convenient to use a value of 1 for x in order to find that constant. Fortunately, there is a table entry with x = 1, so all you have to do is copy that y-value to the answer box.
8 = k·1 . . . . . . . y = k·x for y = 8 and x = 1
8 = k
y = 8x
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Additional comment
If you know the relationship is proportional (the problem tells you it is), then any (x, y) pair will tell you the constant of proportionality.
k = y/x
k = 8 = 4/0.5 = 8/1 = 12/1.5 = 16/2