14- + 9 =15 12- + 7=16 18- +3 =12 11-(13- )=7 15-(4+ )=6 7+(14- )=13
14-8+9=15 12-3+7=16 18-9+3=12 11-(13-9)=7 15-(4+5)=6 7+(14-8)=13