Answer:
y = 12
Explanation:
the equation is
y = 3x
You find the constant or proportionality by put y/x
(15,45) is in the form (x,y) The x is 15 and the y is 45. Put this in the form y/x and you get 45/15 or 3. 3 is the constant of proportionality.
y = 3x
y = 3(4)
y = 12