Homework help, please

Which formula gives the area of a triangle? a=1/2(b+h)

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.

Asystem of equations has 1 solution. if 4x-y=5 is one of the equations , which could be the other equation ?