（69.9-4.74-5.16）×6.5
=（69.9-9.9）×6.5
=60×6.5
=390
[3.5+(15-1.5)]×7.6
=（3.5+15-1.5）×7.6
=17×7.6
=129.2
13.75-（3.75+6.48）
=13.75-3.75-6.48
=10-6.48
=3.52
3.68+7.56-2.68
=3.68-2.68+7.56
=1+7.56
=8.56