questioner wrote:

Hi! Could you please kindly explain to me why it's × 100 ? Thanks!

Let's look at the whole step 2:

2. Same people make 30% of all fishermen.

30% of fishermen = 300 pers.

(30/100) ×

*fishermen* = 300 pers.

*fishermen* = (300 / 30) × 100 pers. = 1000 pers.

So "

× 100" came from the initial "

(30/100) ×".

30/100 is just one of many ways to write down a percentage value:

30/100 = 0.30 = 0.3 = 30%. All these notations define the same value.