Answer
$x=-15 $
Work Step by Step
RECALL:
$\log_a{b} = y \longrightarrow a^y=b$
Use the rule above to obtain:
$\log_2{(1-x)}=4
\\\longrightarrow 2^4 = 1-x
\\16=1-x$
Subtract $1$ on both sides of the equation to obtain:
$16-1=-x
\\15=-x$
Multiply $-1$ on both sides of the equation to obtain:
$-15 =x $
