45-2028+6 14-534-6
35+(21+9) 35+21 67-(4-3) 67-4
□○□=□
□○□○□=□
56-6= 34+5= 79-50= 63-20=.
36-9= 46-7= 23+7= 25+7=.
7+7+7= 15-(6+6)=.