What is X? I literally forgot how to do this lol

Michael is training for a marathon. in his first week he plans to run 8miles. what path should he take

The number of calories you burn depends on your weight. a 110-pound person burns 163 calories during 30 minutes of tennis. find the number of calories that a 190-pound person would burn during the same activity, assuming they burn calories at the same rate.

Gabrielle's age is two times mikhail's age. the sum of their ages is 84. what is mikhail's age?