They would be proportional when y= kx, k is a constant, so, y=2x - 3 is non- proportional. In mathematics, two variables are proportional if a change in one is always goes with a change in the other. They are prop. If one variable is always the product of the other and a constant, but in the equation above the y is not just a product of the x and a constant (2). It's a product of the x and a constant 2 minus 3.
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