there are 60 seconds in 1 minute.
there are 60 minutes in 1 hour.
so in 1 hr there are 60 * 60 seconds, 60 minutes 60 times :).
so 1 hr has 3600 seconds then.
how many seconds in 17 hours? well just 17 * 3600, their product.
we know the photon can do 3x10⁸ meters in one second, namely 300000000 m/s.
so, how many meters did it travel in 17 hours?
well, we know 17 hours is (17*3600) seconds
so, we can say, how many seconds did the photon travel in (17*3600) seconds? we know it can do 3x10⁸ in 1 second alone.
so the distance travelled is just their product, (17*3600) * 300000000.
so is really just 18360000000000 meters, or in scientific notation, there are 10 zeros and then we move the dot over 3 more slots in front of the "1", 1.836 x 10¹³.