You need a 15% alcohol solution. on hand, you have a 210 ml of a 35% alcohol mixture. how much pure water will you need to add to obtain the desired solution?

280 mL

Step-by-step explanation:

If x is the amount of 35% solution and y is the amount of pure water, then:

0.15 = (0.35x + 0y) / (x + y)

0.15 = (0.35x) / (x + y)

Given that x = 210 mL:

0.15 = (0.35×210) / (210 + y)

210 + y = 490

y = 280