13.4-4.68-5.32-1.34
=13.4-（4.68+5.32）-1.34
=13.4-10-1.34
=3.4-1.34
=2.067.24-6.4+3.76+6.4呢？7.24-6.4+3.76+6.4=（7.24+3.76）+（6.4-6.4）=1118.81-（9.8+2.29）18.81-（9.8+2.29）=18.81-9.8-2.29=9.01-2.29=6.72