(1+2)÷3=1[(1+2)÷3+4]÷5=11×2+3+4+5-6-7=1
(1+ 2)÷ 3=1(1+ 2)X 3÷( 4+ 5)=1(1+ 2 +3+ 4)÷ 5 +6- 7 =1
(1+ 2 )/3=1[(1+ 2 )/3+4]/ 5=1{[(1+ 2 )/3+4]/ 5+6} /7 =1
(1+2)/3=11+2-3-4+5=1(1+2-3+4-5)*6+7 =1