9 * 7; 49 : 7; 12 : 3 * 5; (39 + 9) : 8.
9 * 7 = 63; 49 : 7 = 7; 12 : 3 * 5 = 4 * 5 = 20; (39 + 9) : 8 = 48 : 8 = 6.