4 & 5 plz

im stuck on this quiz

How to do this , and can some one explain

An arc subtends a central angle measuring 7pi/4 radians what fraction of the circumference is this arc?

Suppose that one doll house uses the 1 inch scale, meaning that 1 inch on the doll house corresponds to 1/2 foot for life-sized objects. if the doll house is 108 inches wide, what is the width of the full-sized house that it's modeled after? in inches and feet.