=300÷3×2
=100×2
=200
=26×(400÷5)
=26×80
=2080
=47×100-1
=4700-1
=4699
9×9+19=9×9+9+10=9×(9+1)+10=9×10+10=(9+1)×10=10×10= 100
99×99+199