6 * 18 = 6 * (20 - 2) = 6 * 20 - 2 * 6 = 120 - 12 = 108
6 * 18 = 6 * (10 + 8) = 6 * 10 + 6 * 8 = 60 + 48 = 108
23 * 7 = (20 + 3) * 7 = 20 * 7 + 3 * 7 = 140 + 21 = 161
23 * 7 = (30 - 7) * 7 = 30 * 7 - 7 * 7 = 210 - 49 = 161
136 : 8 = (80 + 56) : 8 = 80 : 8 + 56 : 8 = 10 + 7 = 17
136 : 8 = (160 - 24) : 8 = 160 : 8 - 24 : 8 = 20 - 3 = 17
312 : 12 = (240 + 72) : 12 = 240 : 12 + 72 : 12 = 20 + 6 = 26
312 : 12 = (360 - 48) : 12 = 360 : 12 - 48 : 12 = 30 - 4 = 26
:)