How many neutrons does an element have if its atomic number is 50 and its mass number is 166

What overall charge must all compounds have

Mike and mitchell decide to have a foot race. they mark off a stretch of 100 yards, and recruit cindy to work the stopwatch. after running the race and looking at the results, cindy declared that mitchell was the fastest. so how did the boys times compare?

Stoichiometry- i need with 14 and 15! an explanation would be appreciated!