四则混合运算是哪四则

简介：Although the sound of artillery and shouts of death outside the city lasted for a day, and it sounded like a fierce battle, the Ming army's defense line remained motionless. Standing at the top of Jinzhou City and watching, in addition to the numerous turrets and endless trenches of the Ming army, , but no reinforcements could be seen to break through the Ming army's defense line.