What number is not a common factor of 15, 45, and 90

Draw a tape diagram to represent each situation. for some of the situations, you need to decide what to represent with a variable andre bakes 9 pans of brownies. he donates 7 pans to the school bake sale and keeps the rest to divide equally among his class of 30 students

How many sides does a regular polygon have if each exterior angle measure is 45 degrees explain your answer, i really don't understand this.

Tom can paint the fence in 12 hours, but if he works together with a friend they can finish the job in 8 hours. how long would it take for his friend to paint this fence alone?