Convert them into improper fractions and then get a common denominator.
18 1/9 = 163/9
13 5/6 = 83/6
The least common multiple between 9 and 6 is 18.
163/9 x 2 = 326/18
83/6 x 2 = 249 / 18
Now subtract 326 from 249.
[tex]326 - 249 = 77[/tex]
77/18 simplified is 4 5/18.
