Question 647220
Call the distance between sun and mercury x. Then:

Distances:
sun to mercury:  x
sun to venus:    x+31.2   
sun to earth:    x+57

Added all together, they equal 196.2 mi so:

x + x+31.2+x+57=196.2
3x+88.2=196.2
3x=108 mi
x = 36 mi


Substitute this value back into the original equation to make sure it is correct.