Im having some issues understanding an example in my book, mainly due to the fact that there is some missing explanation of what was done. The idea is I need to eventually use something similar to this to for another question to solve a minimum cost optimization problem.

A man launches his boat at point A on a straight river, 3km wide and wants to reach point B, 8km downstream. He can row at 6km/h and run at 8km/h

Rowing distance is

Running distance is

Find where x = 0

Im guessing in the example we want to land part to be on the other side which is why its moved over.

This is where I get confused, Im not sure what exactly has happened, but I think we have some how canceled the top of the left side fraction than halved both sides.

From here Im guessing we square both sides to remove the square root.

Than remove the square root from the right so subtract the left sided one

The square root both sides