She paid 51 dollars in total, so the 51 must be the equation answer. That limits it down to Yellow or Red. It cant be red as she paid 5 dollars per hour, meaning each hour a new 5 will be added to the question. 11 in the equation is just a starting rate that is added on and is never duplicated.
idk if you need this but if you multiply 5 by 8, plugging that into the questions it equals 51=51 so x is 8
