If you would like to know the equation for the above expression, you can calculate this using the following steps:
x ... the number
x * 1/3 inches = 5/6 inches
x * 1/3 = 5/6 /*3/1
x = 5/6 * 3
x = 5/2 = 2 1/2
The correct result would be x * 1/3 inches = 5/6 inches