Step 1
We can't subtract two fractions with different denominators. So you need to get a common denominator. To do this, you'll multiply the denominators times each other... but the numerators have to change, too. They get multiplied by the other term's denominator.
So we multiply 1 by 11, and get 11.
Then we multiply 1 by 9, and get 9.
Next we give both terms new denominators  9 × 11 = 99.
So now our fractions look like this:
