1.3-2加括号2.9+12加括号3.7*9+12加括号
①7x9+12÷(3-2)②7x(9+12)÷3-2③(7x9+12)÷3-2
①(3-2)②(7+12)③(7×9+12)
1.(3-2)2.(9+12)