Question

Im mixing a galloon bucket of windo cleaner i must mix 1 part cleaner to 3 part water how much cleaner do i use

Answer 1

1 part + 3 parts = 4 parts
Divide the gallon into 4 parts.
1/4 of a gallon is 1 quart
You use 1 quart of cleaner.

Answer 2

Lets make a gallon in ounces. 
1 G = 128 Ounces.
Now lets divide by 4: 
128/ 4 = 32
So one part cleaner is 32 ounces. 
3 parts water is 96 ounces. 
96 + 32 = 128