Answer
x=3.86
Work Step by Step
Set the product of the means equal to the product of the extremes and solve for the variable.
$9\times12=4x \times7$
$108=28x$
$108\div28=28x\div28$
$3.8\underset\uparrow5714=x$
Since the digit to the right of the 3rd significant digit is greater than 5, roiund up.
