Question 219776
(15*.20)-(x*.20)+x=15*.40
3-.2x+x=6
.8x=6-3
.8x=3
x=3/.8                     
x=3.75 gal. of pure antifreeze is used.
Proof:
3-3.75*.20+3.75=6
3-.75+3.75=6
6=6