[tex]x-\ Jan's\ destination\\\\y-\ Mya's \ destination \\\\ z-\ Sara's\ destination\\\\\
x+y+z=64\\
x=y\\
z-8=2x\\\\
x+x+z=64\\
z=2x+8\\\\
2x+2x+8=64\\\\
4x+8=64\\\\
4x=64-8\\\\
4x=56\ \ |:4\\\\x=14\\\\z=2x+8=2*14+8=28+8=36\\\\ Sara\ ran\ 36\ miles.[/tex]