解:342-297+158=(342+158)-300+3=500-300+3=203
342-297+158=342-300+3+158=42+1+160=43+160=203
342-297+158=(340+2)-(300-3)+158=340+160-(300-3)=500-300+3=200+3=203
解:342-297+158 =(342+158)-297=500-297=500-300+3=203