The equation below describes a proportional relationship between x and y. What is the constant of​ proportionality?

k=2/5

Step-by-step explanation:

It is the ratio of the amounts y and x:  

k = y/x

Put another way: y = kx

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18

because that’s us why