He is busy right now, so she can't help them

He is busy right now , so she can't help them
$\Rightarrow$If he 
I am not you , so I can't tell him the truth 
$\Rightarrow$If I
She didn't pay attention to his cooking so the food was horrble
$\Rightarrow$If she 
I'm not a rich businessman I can't afford to by an expensive car
$\Rightarrow$If I