1.1.2 ÷ (1 - 80%) = 1.2 ÷ 0.2 = 6
答：这个数是6.
2.45 × (1 + 6%) + 0.5 = 47.7 + 0.5 = 48.2
答：这个数是48.2
3.60% ÷ (1 + 60%) = 0.6 ÷ 1.6 = 37.5%
答：乙数比甲数少37.5%.