Answer:
A 10
Explanation:
a proportional relationship is defined as
y = kx
k is the constant of proportionality, because it is constant for this function for any value of x.
it is usually called the slope of the line or rate of change.
these are special lines : lines that go through the origin (0, 0).
and for these lines people often call k the constant of proportionality.
as we can see right in the given equation, this constant of proportionality is 10.