-= 20÷= 0.77+0.23= +2-+2=
0.3÷0.5= ×7.2= 4000÷80= 1.5×4+6=
×12=
0.4﹣0.25=
0.25×4=
42÷ =
1.5÷0.5=
﹣ =
+ =
31×497≈
=
+=17
+=