Roger makes 70 gallons of pink paint by mixing 21 gallons of white paint. what part of every gallon is from red paint?

There are 49 gallons of red paint.
I figured it out by doing the following:


If you subtract the gallons of pink paint (21) from the total number of gallons (70), then you get the number of gallons of red paint (49) because 49 + 21 = 70. I hope that helps :)

Documentation and time management