÷ = × = - =
+ = 15× = ÷ =
+= -= 15×= 2.1÷=
8÷= ×= ÷10= 1.5÷0.3=
(+)×12= 7×÷7×=
7×= ×= ×= 2×1= =
×21= 51×= ×25= = ×3=
够□ 不够□