.4 is tenths .42 is hundredths and .422 is thousandths
You can solve this problem through factoring.
First, you have the equation,

Then, you can factor the numerator.

You can cancel out the x-6 in both the numerator and the denominator because they would equal to just 1.
You are left with 
The function is removable noncontinuous at x=6 because if you plug in 6 in x-6, your denominator would be undefined.
Answer:
y = 6 when x = 18
Step-by-step explanation:
The appropriate formula for this direct proportion is y = kx, where k is the constant of proportionality.
We know y = 3 when x = 9: 3 = k(9)
This yields k = 3/9, or k = 1/3
Then the formula is y = (1/3)x
and when x = 18, y = (1/3)(18) = 6
y = 6 when x = 18