7. 80-16*5 70+2*12 90:(6*15) 68:(72:18) 78:(13-7)*0 64:(39-7)*1

80 - 16 * 5 = 80 - 80 = 0 70 + 2 * 12 = 70 + 24 = 94 90 : (6 * 15) = 90 : 90 = 1 68 : (72 : 18) = 68 : 4 = 17 78 : (13 - 7) * 0 = 78 : 6 * 0 = 13 * 0 = 0 64 : (39 - 7) * 1 = 64 : 32 * 1 = 2 * 1 = 2