课件14张PPT。乘车++=57223=8-413-455-=+9110XXTQ练一练=8233--4 + 1 - 5=7 - 2 - 3 =4 + 1 + 5 =8 - 6 + 4 =505251026练一练6.10 - 8 +5 =4+2 +1 =10 - 7 -3 =10 - 8 + 5 =6 -3 + 7 =3 + 5 - 6 =2 + 7 + 1 =6 - 3 + 7 =7707021010练一练7.2 + 2 + 2 + 2 + 2 =10练一练9 - 2 - 2 - 2 - 2 =17.