① x+=
②2x-(+)=
③+-x=1
1.72-0.3=
1.8+0.02=
0.56÷7=
7.73+2.07=
3.5×40=
5÷20=
9.5÷(2.5×4)=
+=
×=
1-=
+2=
×0=
-=