Let's first put 8/9 and 5/12 in simplest form.
We need to have the denominators at the same value by find the greatest common multiple.
The GCM of 9 and 12 is 36. By making both denominators 36, we also have to change the numerator.
36/9 is 4 so the numerator of 8/9 has to be multiplied by 4, making that 32/36.
36/12 is 3 so the numerator of 5/12 has to be multiplied by 3, making that 15/36.
Now, that we have the same denominators, we can subtract.
32/36-15/36 can be done simply by just subtracting the numerators together. Remember, the denominators stay the same.
32/35-15/36 = 17/36
Since there is no least common multiple of 17 and 36, then 17/36 is the final answer.
