33×66+99+78=33×3×22+99+78=99×22+99+78=99×（22+1）+78=（100-1）×23+78=100×23-23+78=2300+（78-23）=2300+55=2355
33×66+99+78＝33×66+33×3+78＝33×(66+3)+78＝33×69+78＝33×（70-1）+78＝33×70-33+78＝2310-33+78＝2355
