17.24-3.98=17.24-（4-0.02）=17.24-4+0.02=13.24+0.02=13.26
17.24-3.98=17.24-4+0.02=13.24+0.02=13.26
17.24+2-3.98+2=17.26-4=13.26
17.24-3.98的简算怎么做？=17.24-4+0.02=13.26
