Ответ:13 − 5 = 8; 13 − 8 = 5; 11 − 9 = 2; 12 − 9 = 3; 13 − 7 = 6; 4 + 8 = 12; 7 + 5 = 12; 6 + 7 = 13; 7 + 4 = 11.