kathazeleyes74 kathazeleyes74 02-01-2019 Mathematics contestada 6. Write the following proportion using colons. 7 is to 21 as 3 is to 9. A. 7:21 = 3:9 B. 7:3 = 21:9 C. 21:7 = 3:9 D. 7:21 = 9:3