Chapter 11 - Systems of Equations and Inequalities - 11.3 Systems of Linear Equations: Determinants - 11.3 Assess Your Understanding - Page 742: 7

$22$

We know that for a matrix \[ \left[\begin{array}{rr} a & b \\ c &d \\ \end{array} \right] \] the determinant is $D=ad-bc.$ Hence, here we hvae $D=(6\cdot3)-[4\cdot(-1)]\\ D=18-(-4)\\ D=18+4\\ D=22$