https://youtu.be/Q0tTfe2lKIc?t=184
I am confused as to how the hours ends up in the "numerator" (to the side of the equation which as I understand it is the same as in the numerator). Things I "know":
You can think of any number as itself divided by 1.
You can convert nested division problems by multiplying by the reciprocal.
What I think I'm struggling with is: the rules for when/where you can consider a number divided by 1 and then use it's reciprocal to multiply.
For instance as I understand this part of the equation:

w km
---------
5 km / h

km cancels out leaving

w
-----
5 1/h

which is the same as

w
-
5
-
h

I can imagine a couple ways to manipulate this. I am not sure which are valid.

w
-
1
-
5
-
h

which could be rewritten as

w   h
- * -
1   5

which is the same as

wh
--
5

which is the same as

w
- h
5

As far as I can tell this is what was done in the video. I am okay with this until I try to prove to myself that I am allowed to do this at which point I become confused.

Another method I can imagine to manipulate this is:

w
-
5
-
h
-
1

which can be rewritten as

w   1
- * -
5   h

which is the same as

w
--
5h

This seems valid but doesn't result in the h being in the numerator like I want.

In the past when I was unsure of what is valid algebraically I would test by plugging in random numbers for variables and then solve the equation with various methods to see which methods are valid. I tried to do that here.

Let w=2, h=3

Now:

w
-
5
-
h

is the same as

2
-
5
-
3

plugging "2/5/3" into the calculator = about 0.13

I then try to test the aforementioned methods to see which are valid

w   h
- * -
1   5

is the same as

2   3
- * -
1   5

is the same as

6
-
5

which = 1.2 which is NOT the same as 0.13 which means this method must NOT be valid? This is where I am confused. How is this not valid but is apparently what is used in the video to get the correct answer?

When I try the other method:

w
-
5
-
h
-
1

is the same as

2
-
5
-
3
-
1

is the same as

2   1
- * -
5   3

is the same as

2
-
15

which = about 0.13
This seems to be a valid statement but does not help me to move the h to the numerator.

What are the rules for working with something like:

a
-
b
-
c
-
d
-
e
-
f

?

Can you do:

a
-
b   f
- * -
c   e
-
d

?

What about:

a
-   e
b * - / f
-   d
c

?

What about:

a
-
b
-   1
c * -
-   f
d
-
e

?

How can I find resources to better understand this? Most of what I've been coming across are how to solve complex fractions which include addition and subtraction or how to solve division of fractions where there are only 2 fractions being divided by each other...in which case just flip the button and multiply.