简算 198×456 7÷4--4÷7 605×99＋605

198×456
=(200-2)×456
=91200-912
=91200-1000+88
=90288
7÷4--4÷7
=1+3/4 -(1-3/7)
=3/4-3/7
=3×(7-4)/28
=-9/28
605×99＋605
=605×(99+1)
=60500