Answer
$x=0.4,y=-1$
Work Step by Step
Cramer's Rule for $2$ equations in $2$ unknowns says that the system of linear equations is equivalent to the matrix equation $DX=B$ and if $|D|\ne 0$, then the solutions are $x_i=\frac{|D_{x_i}|}{|D|}$ where $D_{x_i}$ can be obtained by replacing the $i$th column of $D$ by $B$
Hence, we have:
$|D|=10(-31)-(-17)(20)=30$
$|D_x|=21(-31)-(-17)39=12$
$|D_y|=10(39)-(21)(20)=-30$
Thus
$x=\frac{|D_x|}{|D|}=0.4,y=\frac{|D_y|}{|D|}=-1$
