①由题意可知,⑴班捐a件,∵⑵比⑴多40,∴⑵=a+40,同理可知,⑶=2（a+40)×2=2a+80
②由题意可知,⑵-⑴=40,∴40为多出部分,又∵⑴=a,∴⑵比⑴多40/a
③⑵=（a+a+40+2a+80）=a+30