Plot the nonzero multiples of the numerator and the denominator on separate number lines

I don't see any fractions. 

Let's me make up an example: 
8/12 

Non-zero multiples of 8: 
1 x 8 = 8 
2 x 8 = 16 
3 x 8 = 24 
4 x 8 = 32 
5 x 8 = 40 
etc. 

Non-zero multiples of 12: 
1 x 12 = 12 
2 x 12 = 24 
3 x 12 = 36 
4 x 12 = 48 
etc. 

Plot the multiples on two parallel number lines. You'll see that 24 is the first place where they share a multiple. That's the "least common multiple" of those two numbers. 

LCM(8,12) = 24

Number nine is f(x)= 40x : ) hoped i ya