Answer:
Being proportional between two entities, refers to the 'Constant of Proportionality' that would be fixed between them which establishes a relationship between them when multiplied or divided.
If we considered it on a graph, the 'Constant Of Proportionality' may take any real values between the coordinate pairs x and y [x,y]. As even 0 is a real number, it will surely be a constant of proportionality when multiplied since its product would result in itself (0). Hence, both x and y turns 0.
As the coordinates of the origin are always (0,0), the graph (Or the slope) would surely pass through the origin.
Example :
If we consider a graph such that x=y.
And if we multiply or divide any real number (a) between them.
ax=ay
As a is a variable, and can take the value of 0, the graph can pass through the origin as x and y nullify becoming the coordinates of the origin.
