Question

The average distance from the sun to Pluto is approximately 6.10 × 109 km. How long does it take light from 

Answer 1

$V= \frac{S}{t}$
$t= \frac{S}{V}$<u />
$t= \frac{S}{c}$
$t= \frac{6.1*10^{12}}{299792458}$
$t=20347.4098071s$

It takes 20347.4098071s for light from the sun to reach Pluto.
The 6.1*10^9 is replaced by 6.1*10^12 on line 4 because we convert the distance from km to m. 
c = speed of light. If a different value was given in the previous question then use that instead of the value I used to do the final calculation.