Joshua's cousin pledged $12 for a charity walk if joshua walk 3 miles how much did his cousin pay for per mile

What number must you add to complete the square x^2+12x=16

The inside wheels of a car traveling on a circular path are rotating half as fast as the outside wheels. the front two wheels are six feet apart. what is the number of feet in the path traced by the inside front wheel in one trip around the circle? express your answer in the form "k \pi", where k is an integer.

Having a hard time understanding this question (see attachment).