20 = 10 x 10 = 100 x 2 = 200
40 = 200x2 = 400
60 = 200x3 = 600

Here's the solution :
therefore , correct choice is B
Answer:
3 : 7 : 5
Step-by-step explanation:
Given
12 : 28 : 20 ← divide each part by 4 ( the LCM of 12, 28, 20 )
= 3 : 7 : 5
Answer: if rounded like 68 18/100%
Step-by-step explanation: