Answer
The television's price before the reduction is $ \$ 420$.
Work Step by Step
Let $ x $ represents the television's price before the reduction.
$ 20 \% $ of the television's price is $ = (0.20)x $.
The price of the television after reduction is $ \$ 336 $.
In mathematical form.
$ x-0.20x=336 $
$ (1-0.20)x=336 $
$ 0.80x=336 $
$ x=\frac{336}{0.80} $
$ x=420 $.