First of all, you English grammar needs help, too.
A sentence begins with a capital letter and the subject and verb must agree.
First, change the mixed number to an improper fraction and then divide to get a rate: miles/hr = mph
12 5/6 = 77/6 miles
(77/6)/(2/3) -- invert and multiply => 77 * 3 /(6 * 2) =77/4 = 19 1/4 mph
