=16.51-12.1+3.87=16-12+3+0.51-0.1+0.87=7+0.41+0.87==7+1+0.41-0.13=8+0.41-0.11-0.02=8+0.30-0.02=8+0.28=8.28
16.51-(12.1-3.87)
=16.51-12.1+3.87
=4.41+4-0.13
=8.4-0.12
=8.28
16.51-(12.1-3.87)=16.51-12.1+3.87=8.28
16.51-(12.1-3.87)
=16.51-12.1+3.87
=4.41+3.87
=8.28