用简便计算99X56=100×56-56=5600-56=5544
(99十1)Ⅹ56-56=100x56-56=5600-56=5544
（100-1）×56=100×56-1×56=5600-56=5544
99ⅹ67+67:=100ⅹ56-56=5600-56=5544
