Question

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

Answer 1

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