This is a bad example because no broker would force you to sell your own equity.

You had 100 dollars, you're leveraging 50 cents for every dollar you put in giving you a .5:1 leverage ( or 50%, or 1.5/1 as a fraction)

Only if the stock loses more than 100 dollars in your equity would the broker be worried and ask for margin. This means your $150 dollars of leveraged stock would have to drop to $50 dollars before the broker would be worried and sell your stock to get their $50 back. This means your stock could drop 66,7% or 2/3 as a fraction.

All fees are paid upfront and the rest from your margin. Not your stock.