Question 742226
we are given:

If you have 500 ml of 28% salt-solution, how many milliliters of it should you mix with water in order to create 250 ml of a 17% salt-solution?

you correctly stated that

.28 * 500 = 140   and
.17 * 250 = 42.5

so we are looking for the solution to

140/500 = 42.5/x

cross multiply and we get x =151.79 ml


140x = 500*42.5
x = 151.79 ml