A biologist has two brine solutions, one containing 9% salt and another containing 36% salt. How many milliliters of each solution should she mix to obtain 1 L of a solution that contains 25.2% salt?

Explanation:

The mass of salt is constant.

You have two conditions

(a) Mass of salt in 9 % + mass of salt in 36% = mass of salt in 25.2 %

(b) Volume of 9 % + Volume of 36 % = volume of 25.2 %

Let x = volume of   9 %

and y = volume of 36 %

Check:

It checks.

the answer would be c

answer; 4 electrons;