两位数减一位数退位减法100以内口算题

20-5= 70-5= 53-6= 24-7= 49-8= 37-5= 39-5= 26-8= 50-7= 40-6= 54-9= 53-9= 49-9= 37-6= 39-6= 77-9= 40-3