Concept:Let the third number be x, then express the two numbers as percentages above x.Explanation:Let the third number be x.First number is 20% more: x+20% of x=x+0.2x=1.2x.Second number is 50% more: x+50% of x=x+0.5x=1.5x.The ratio is 1.2x:1.5x=1.2:1.5.Multiply both terms by 10 to remove decimals: 12:15.Divide both terms by 3: 4:5.Alternatively, divide 1.2 and 1.5 by 0.3 giving 4 and 5 directly.Thus the ratio simplifies to 4:5.Answer:4:5