Option C
The equation used to solve the problem is 
<em><u>Solution:</u></em>
Given that, A plane traveled at a constant rate of 500 kmph
To find: time taken to travel 1700 km
Also given that,
<em>The distance formula states that distance (d) is equal to the product of rate (r) and time (t)</em>


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

Thus the equation used to solve the problem is 
Thus option C is correct