如图,DE∥BC,EC=AD,AE=2cm,AB=7.5cm,求DB的长.
在这人世间,有些路是非要单独一个人去面对,单独一个人去跋涉的,路再长、再远,夜再黑、再暗也得独自默默地走下去。——席慕蓉
— Do you know if we will go for a picnic this Saturday?
— I think we will if we ________ any classes.