Two solutions of different concentrations of acid are mixed creating 40 ml of a solution that is 32% acid. one-quarter of the solution is made up of a 20% acid solution. the remaining three-quarters is made up of a solution of unknown concentration,  c. which equation can be used to determine  c, the unknown concentration? 30c  +  10(0.2)  =  40(0.32)(c)  +  (0.2)  =  40(0.32)(c)(  (0.2))  =  40(0.32)30(c)(10(0.2))  =  40(0.32)