First observe the calculation process of the first two questions, and then follow the calculation of the second two questions. 9 * 9-1 = 9 * (10-1) - 1 = 9 * 10-9-1 = 90-10 = 80 9*9-1=9 *（10-1）-1=9*10-9-1=90-10=80 98*9-2=98（10-1）-2=980-98-2=980-100=880 987*9-3=（ ） 9876*9-4=（ ）

First observe the calculation process of the first two questions, and then follow the calculation of the second two questions. 9 * 9-1 = 9 * (10-1) - 1 = 9 * 10-9-1 = 90-10 = 80 9*9-1=9 *（10-1）-1=9*10-9-1=90-10=80 98*9-2=98（10-1）-2=980-98-2=980-100=880 987*9-3=（ ） 9876*9-4=（ ）

987*9-3=（ 987*（10-1）-3 = 987*10 - 987-3 = 9870 - 990 = 8880 ）9876*9-4=（ 9876*（10-1）-4 = 9876*10 - 9876 - 4 = 98760 -9880 = 88880 ）(*^__ ^* *^__ ^* *^__ ^*If you don't understand, you can continue to ask this question, online at any time