Mathematics

# what is the value of the special determinant Dy (from Cramer's Rule)? Enter the numerical value only. x - 2y = 2 2x + y = 9

$\left\{\begin{array}{ccc}x-2y=2\\2x+y=9\end{array}\right\\\\\\D_y= \left|\begin{array}{ccc}1&2\\2&9\end{array}\right|=1\cdot9-2\cdot2=9-4=5$