Question Number 74328 by arthur.kangdani@gmail.com last updated on 22/Nov/19
Answered by ajfour last updated on 22/Nov/19
$${x}=\frac{\begin{vmatrix}{\mathrm{10}}&{\mathrm{2}}&{\mathrm{4}}\\{\mathrm{4}}&{\mathrm{10}}&{\mathrm{7}}\\{\mathrm{9}}&{\mathrm{5}}&{\mathrm{16}}\end{vmatrix}_{} }{\begin{vmatrix}{\mathrm{6}}&{\mathrm{2}}&{\mathrm{4}}\\{\mathrm{9}}&{\mathrm{10}}&{\mathrm{7}}\\{\mathrm{12}}&{\mathrm{5}}&{\mathrm{16}}\end{vmatrix}^{} } \\ $$$$\Rightarrow\:\:{x}=\frac{\mathrm{10}\left(\mathrm{160}−\mathrm{35}\right)−\mathrm{2}\left(\mathrm{64}−\mathrm{63}\right)+\mathrm{4}\left(\mathrm{20}−\mathrm{90}\right)}{\mathrm{6}\left(\mathrm{160}−\mathrm{35}\right)−\mathrm{2}\left(\mathrm{144}−\mathrm{84}\right)+\mathrm{4}\left(\mathrm{45}−\mathrm{120}\right)} \\ $$$$\:\:\:\:\:{x}=\frac{\mathrm{1250}−\mathrm{2}−\mathrm{280}}{\mathrm{750}−\mathrm{120}−\mathrm{300}}\:=\:\frac{\mathrm{968}}{\mathrm{330}}\:=\:\frac{\mathrm{88}}{\mathrm{30}} \\ $$$$..... \\ $$