已知单项式3amb2与﹣ 23 a4bn﹣1是同类项,那么m﹣3n=____.
There is a clock.
如图,是由三个正方形组成的图形,则∠1+∠2+∠3等于( )
—May I speak to Mr. Smith?
— ,please.I'll see if he is in.