Answer:
31.5 litres
Explanation:
If Mel uses all 30 litres of yellow paint, then:
5 / 2 = 30 / x
5x = 60
x = 12
Mel would need 12 litres of blue paint, but she only has 9 litres. So the amount of yellow paint she needs is:
5 / 2 = x / 9
2x = 45
x = 22.5
Mel will use 22.5 litres of yellow paint with 9 litres of blue paint to make a total of 31.5 litres of green paint.