小兔和小狗在草坪上踢足球,它们的书包放在了大树下。啄木鸟看到书包里露出了一个作业本,打开一看,里面有这样几道题:嗯?啄木鸟的眼睛一下子瞪大了,这是怎么回事?啄木鸟对着草坪喊道:“嗨,小伙子,你这儿有虫子了!”小兔和小狗听到喊声,连忙跑了过来:“虫子在哪儿?”啄木鸟指着这两个算式说:“它们就是虫子!”“这怎么可能?”小兔和小狗都不相信。啄木鸟解释说:“在笔算两位数减两位数的退位减法 Bunnies and puppies play football on the lawn, their school bags are placed under the tree. Woodpecker saw the bag revealed a homework, opened the look, there are a few questions: ah? Woodpecker's eyes suddenly wide, what's going on? Woodpecker shouting to the lawn: ”Hey, The young man, you have a bug here! “” The bunny and the puppy heard the shout, and quickly ran over: “Where is the bug?” The woodpecker pointed to the two formulas: “They are bugs!” “How is this possible?” Bunny and puppy do not believe. Woodpecker explained: "in the calculation of double-digit double-digit absentee subtraction subtraction