Step-by-step explanation:
Ratio of decrease in red paint = 7/10
Amount of red paint to be used now = Previous amount of red paint * Ratio of decrease
Amount of red paint to be used now = 400ml * (7/10)
Multiplying the values, we get:
Amount of red paint to be used now = 280 ml
Therefore, Danni should use 280 ml of red paint in the new mix.