Answer:
$55.55
Explanation:
In order to calculate the original price of the radio we just have to do a rule of thirds, we know that the price payed was $50, and that it was 10% off from the original price, now we just have to to a simple rule of thirds, if $50 is the 90% how much is the 100%?

Now we clear X to find how much is the 100%:

So the original price was $55.55