You mix 2/5 cup of red paint for every 1/4 cup of blue paint to make 15 /8 gallons of purple paint. how much red paint and blue paint do you use?

a- 2/5 + 1/4=.65 mixture of red and blue paint
(2/5) / .65 X 1.625=1 gallon of red paint
(1/4) / .65 X 1.625=5/8 gallons of blue paint, because
1 + 5/8=1 5/8 gallons of purple paint.

b-1/10 + 2/5 + 1/4=.75 mixture of white, red and blue paint

***FINAL 1 gallon red, 5/8 gallon blue.***