Answer
$x=\frac{2d-b}{a-2c}$
Work Step by Step
$\displaystyle \frac{ax+b}{cx+d}=2$
We cross-multiply:
$ax+b=2(cx+d)$
And distribute:
$ax+b=2cx+2d$
And move $x$ terms to one side:
$ax-2cx=2d-b$
And factor out $x$:
$(a-2c)x=2d-b$
And solve for $x$:
$x=\frac{2d-b}{a-2c}$