Question

If the earth was 10 times farther away from sun which planet is closest.

Answer 1

the distance from sun to earth is sometimes known as 1 'Astronomical unit' (AU)

look up on google which planet has an orbit of closest to 10 AU

While YOU are doing that research you will probably learn some other interesting stuff about the planets! :-)

Answer 2

Here is a good place for you to start:
http://www.universetoday.com/15462/how-far-are-the-planets-from-the-sun/