9.9×4.5+0.99×56-0.99
=0.99(45+56-1)
=0.99*100
=99
8.9×1.24×8.9÷1.24
=8.9*8.9
=(9-0.1)*(9-0.1)
=81-2*9*0.1+0.01
=79.21
128+306÷17×9
=128+18*9
=128+162
=290