①x-= ②(-)-x=
1-=
+=
-=
2+=
=
28
50
83
49
90
67
1800-799= ×0= 354+147≈
10-10%= 3.6 +1.8= ×5.6= 723÷89≈
2÷= 12.3+7 = 0.23= 0.125×17×8=