It’s either B or D. I’m sorry I’m not so sure but I think it’s either one of those.
First, find the amount of time is taken to travel 1 mile :
time taken to travel 1 mile = 20/6 = 3 ⅓ mins
hence, time taken to travel 9 miles = 3 ⅓ x 9 = 30 mins
time taken to travel 10 miles = 3 ⅓ x 10 = 33 ⅓ mins
Your answer is -1/2
and this is done by simplyfing