what is this 'method' called? maths

[builder22]

this is probably basic but it's doing my head in!

8000*4 = 3800*x finding x with cross multiply and divide makes sense...
8000*4 = 3800*x so 32000 = 3800*x so x = 32000/3800 = 8.42105

this method also works, but struggling to see exactly why!
3800/8000 = 4/x so 3800/8000 = 0.475, then 4/0.475 = 8.42105

 

[builder22]

meant to write this as the first one...don't thnk it make any difference tho

3800 = 4
8000....x (ignore the dots!)

3800/8000 = 4/x finding x with cross multiply and divide makes sense...
8000*4 = 3800*x so 32000 = 3800*x so x = 32000/3800 = 8.42105

 

[builder22]

ok, thanks for that

maybe a better question would be how would you solve x...the most straight forward way of writing out the solution would be?

3800 = 4
8000....x