5/6x1/13+5/9x2/13+5/18x3/13
=1/13(5/6＋5/9* 2+5/18* 3)
=5/13(1/6+1/9* 2+1/18* 3)
=5/13 * 1/18 (3+4+3)
=5/13 * 1/18 *10
=25/13 * 1/9
=25/117