三七____
____七三十五
____七四十九
七____六十三
如图,梯形ABCD中,AD∥BC,∠ABC=2∠BCD=2α,点E在AD上,点F在DC上,且∠BEF=∠A.
若单项式13a3bn+1和2a2m﹣1b3是同类项,求3m+n的值.
I went to school without ____ (eat) anything this morning.