Since question is incomplete, I will try my best to complete it my way:
It is given that 2 cups of blue with 10 cups of yellow make up green.
Question asks how many cups of yellow would i need to mix with 1 cup of blue to make same shade of green.
So,
2 cup with 10 cup
We divide each by 2, to get:
2/2 = 1
10/2 = 5
This means:
1 cup with 5 cup
Or,
1 cup blue with 5 cup yellow.
So, we arrive at our answer:
with 1 cup of blue, we need to fix 5 cups of yellow to get same shade of green.