hi please help me if you know the answer

Answer:
C. 1.5x=y is the correct answer
Step-by-step explanation:
A. doesn't work after the first value
B. doesn't work either
C. 1.5*20= 30 1.5*30 = 40 1.5*40= 60 1.5*50= 75
D. Doesn't work see: 30-15 doesn't equal 20
hope this helps <3