Answer
$x=5$
Work Step by Step
A 2x2 determinant can be calculated as ad−bc, where a is the upper-left entry, b is the upper-right entry, c is the lower-left entry, and d is the lower-right entry.
Therefore, the value of this determinant is $(1\times7)-(x\times2)=-3$
We can now solve this value for x.
$7-2x=-3$
Subtract 7 both sides.
$-2x=-10$
Divide both sides by -2.
$x=5$