Answer:
Radio waves move at the speed of light which is aproximately 300,000 km per second or 3.8*10^8 m/s
1 ly = 9.461*10^15 m
Then
7.9 light-years = 7.4*10^16 m
By, velocity = distance/ time
time = distance/time
t = 7.4*10^16/3.8*10^8
= 1.9473684*10^24 seconds
Converting seconds to years (1 year = 31536000 seconds)
1.9473684*10^24/ 31536000 years
=6.17096989 ×10^16 years
