Okay, I have the expression:

now I need help to understand how these fractions are added together.

I have the solution to it, but upon analysing it I am a bit confused:

- Why are we multiplying by and how did we get the conclusion to use in the first place.
- Same with and .

I get the rest of it but those two parts of the solution don't make sense to me!? Are they using an Least Common Denominator (LCD) or something?

Thanks in advance.