Answer:
Step-by-step explanation:
"y = 1 5 x" is ambiguous; please do not leave spaces. I'm assuming you meant y = 15x.
If you graph this, you'll see a line with slope 15 that goes through the origin. If there were a y-intercept other than zero, such as in y = 15x + 5, this equation would not represent a proportional relationship.
In summary:
There's a constant ("constant of proportionality") slope, which here is 15.
The line MUST go through the origin.