5 + 3 = 8, so there are 8 pints of pint in total in the mixture.
----------------
| r | r | r | r |
|---------------|
| r |w |w |w |
-----------------
48 ÷ 8 = 6, so there would be 6 diagrams (not that I think you need to draw them all out, but point out that fact).
5 * 6 = 30 pints of red (each diagram holds 5 red pints)
3 * 6 = 18 pints of white (each diagram holds 3 white pints)
