Question 750912
you have 80 ml of a solution that is 60% acid


so you have 80*0.6 = 48 mL of pure acid



Let x = amount of pure acid


If you add x mL of pure acid to 48 mL of pure acid, then you'll have 48+x mL of pure acid total. This is out of 80 + x mL of new total solution.


This ratio (48+x)/(80+x) must be equal to 0.75 since we want this new percentage to be 75%, so


(48+x)/(80+x) = 0.75


now solve for x


(48+x)/(80+x) = 0.75


48+x = 0.75(80+x)


48+x = 60+0.75x


x = 60+0.75x - 48


x-0.75x = 60 - 48


0.25x = 12


x = 12/0.25


x = 48


So you need to add 48 mL of pure acid.