London mixes 6 parts yellow paint with 3 parts blue paint to make green. She adds 1 more part of yellow to change the shade of green. What is the new ratio of yellow to blue?

London starts with 6 parts yellow and 3 parts blue. Adding 1 part of yellow makes 7 parts yellow, while the blue stays at 3 parts. So the new ratio of yellow to blue is 7 to 3, which is choice D.

AI-written and checked against the verified answer.