Answer:
24 quarts
Step-by-step explanation:
45% of 20 is 0.45 * 20 = 9
So in 20 quarts, 9 is pure antifreeze
suppose we want to add x quarts and this will make it 75%. So we can write:
[tex]\frac{9+x}{20+x}=0.75[/tex]
Now we cross multiply, do algebra, and solve for x:
[tex]\frac{9+x}{20+x}=0.75\\(0.75)(20+x)=9+x\\15+0.75x=9+x\\15-9=x-0.75x\\6=0.25x\\x=\frac{6}{0.25}\\x=24[/tex]
Hence, 24 quarts should be added
