Margin call question?

Beginner Questions
1

Hi guys,
I know this Equity=usable margin + used margin
$300=$200+$100 so if i lost 200$ usable margin then E=Used=100$
time for margin call

But just a broker told me if equity / Used Margin 50% , you may get a margin call. How come always E=>used margin and to be 50% must E<used:confused:

2

Remember that margin used (as you put it) is basically the initial margin requirement. It’s pretty common that margin calls come when your equity gets down to half that.

3

I get it now
E=usable+used margin
300$=200+100$ if i lost usable then E=Used margin=100
No margin call yet they told me when E/Used=50% that mean
usable be negative to -50$ it will be E=(-50)+100
"If your losses exceed your usable margin"
I just didn’t thought it could be negative for margin call

Thanks