Answer: The number 0 goes in all three blanks.
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Explanation:
A linear proportional relationship always has a y intercept of 0. Visually, this means the proportional graph will go through the origin. So that in turn means b = 0.
For example, the equation y = 5x is a proportional equation with 5 being the constant of proportion. Whatever x is, multiply by 5 to get y. We can think of y = 5x as y = 5x+0 to see that b = 0 here.
When considering nonproportional equations, we let b equal anything but zero. In other words, b is nonzero in this case. Something like y = 5x+2 is not proportional. The graph doesn't go through the origin and the intercept here is (0,2).
In short, you'll write "0" without quotes into each blank.