http://en.wikipedia.org/wiki/Ellipse#Pla…
Specifically this equation from that section is of use in this problem:
http://upload.wikimedia.org/math/d/f/6/d…
Note that r_p is the radius of nearest orbital distance from the star and a is the average distance given in the problem. This means it's just a plug and chug problem.
r_p = (1 - e)*a
r_p = (1 - 0.5) * (0.722 AU)
r_p = 0.361 AU = 54 million km
3) Find the planet's farthest orbital distance from its star. - Again the previously listed section from wikipedia has all the relevant information. Specifically we want to use this equation now:
http://upload.wikimedia.org/math/8/d/5/8…
In this equation r_a is the farthest orbital distance from the star and again e and a are the eccentricity and average orbital period respectively.
r_a = (1 + e)*a
r_a = (1 + 0.5) * (0.722 AU)
r_a = 1.083 AU = 162 million km
Hopefully this helps you out.