13.2-3.2×1.9=13.2-6.08=7.12
13.2-3.2×1.9＝13.2-3.2×（2-0.1）＝13.2-3.2×2+3.2×0.1＝13.2-6.4+0.32＝13.2+0.32-6.4＝7.12
