What is the value of the ratio 4:5

You might need to be more specific, it could be 4 puppies to 5 dogs, or 4 apples to 5 oranges or 4 cups of flour to 5 cups of flour.

Step-by-step explanation:

The value of 4:5 is 4 for every 5 like 4 cups of sugar for every 5 cups of flour

Part A: For every 1 cup of yellow paint, Garcia mixed 4 cups of red paint to make a shade of orange paint.   
Part B:  Garcia should add 1/4 cup of yellow paint to each cup of red paint to mix the same shade of orange.    
Part C: The unit price for each cup of red paint is $7.  6=$42, divide both sides by 6, 6/6=1, $42/6=$7, so 1 cup of red paint=$7.