Answer:
19.95
Explanation:
Power ratio (in db) = 10 * log [P(out)/P(in)]
Here, P(in) and P(out) correspond to input and output power in Watts respectively.
This implies, 13 db = 10 * log [P(out)/P(in)]
Rearranging, log [P(out)/P(in)] = (13/10)
Or, P(out)/P(in) = 10 ^ 1.3 = 19.95
But, P(out)/P(in) corresponds to the power ratio of output and input power.
So the required power ratio corresponds to 19.95