Answer:
25L
Step-by-step explanation:
Since there is 15 alkali at first, there must be 25-15 = 10 water at first. Since there is 30% alkaline at last, there must be 100-30 = 70% water at last.
Let x = the amount of water added
Using this information we come up with the equation:
[tex]\frac{10+x}{25+x}[/tex] = [tex]\frac{70}{100}[/tex] (10 + x is the amount of water at last, 25 + x is the total liquid, and 70/100 is the percentage of water at last)
using cross-multiply we get:
1000x + 100x = 70x + 1750
solving, we get x = 25