Option C
The equation used to solve the problem is

Solution:
Given that, A plane traveled at a constant rate of 500 kmph
To find: time taken to travel 1700 km
Also given that,
The distance formula states that distance (d) is equal to the product of rate (r) and time (t)


From given information,
rate = r = 500 kmph
distance = d = 1700 km
time taken = t = ?
Substituting the values in above formula we get,

Thus the equation used to solve the problem is

Thus option C is correct