If x and y are proportional, then the quotient y and x is constant.
[tex]\dfrac{y}{x}=a-constant[/tex]
The equation of a Proportional Relationship:
[tex]\dfrac{y}{x}=a\qquad\text{multiply both sides by }\ x\neq0\\\\y=ax[/tex]
Therefore your answer is
D. y = 12.5x
