10.1-2.23
=10+0.1-2.23
=10-2.23+0.1
=7.77+0.1
=7.87
1.004-0.796
=(1+0.004)-(0.8-0.004)
=1+0.004-0.8+0.004
=1-0.8+0.004+0.004
=0.2+0.008
=0.208