[1/2-(3/4-3/5)]÷7/10
=[1/2-(15/20-12/20)]×10/7
=(1/2-3/20)×10/7
=(10/20-3/20)×10/7
=7/20×10/7
=1/2
27.4-52.8÷(1.9+2.1)
=27.4-52.8÷4
=27.4-13.2
=14.2
9.25×9.9+0.925
=9.25×9.9+9.25×0.1
=9.25×(9.9+0.1)
=9.25×10
=92.5