7-21. A chemical engineer is to combine two liquids of differing saline concentrations as shown in Fig. P7.21. If Solution A is 75% saline and Solution B is 25% saline, the combination of both solutions such 216 Chapter 7 Systems of Equations in Engin that the resulting mixture is 60% saline satisfies the system of equations given below, where VA and VB are the vol- umes of each individual solution and VT is the total volume of the mixture. V+VB-V+=0 0.75V +0.25V-0.60V+=0 Suppose that the total volume is V+= 150 gallons: (a) Substitute the value of V, and write the system of equations in the matrix form Ax=b, where x= (b) Find Vand V using the matrix algebra method. Perform all matrix computations by hand and show all steps. (c) Find V and VB using Cramer's rule. (d) Find V and V using substitution. Figure P7.21 Mixture of two saline solutions.