Answer:
5/7 quart
Step-by-step explanation:
Amount = concentration × volume
Amounts added = final amount
100% × x + 20% × 5 = 30% × (x+5)
Solving for x:
1.00x + 0.2×5 = 0.3×(x+5)
x + 1 = 0.3x + 1.5
0.7x = 0.5
x = 5/7
x ≈ 0.7
You should add 5/7 quart of pure antifreeze, or about 0.7 quart.
