（1）2.3x0.16÷2.3x0.16
=2.3÷2.3 x 0.16÷0.16
= 1x1
=1
（2）1.8x0.9+0.18-18x0.1
=1.8 x (0.9 + 0.1 - 1)
=1.8 x 0
=0
（3）1.8x0.9+0.18
=1.8 x (0.9 + 0.1)
=1.8 x 1
=1.8