Answer: 1/21
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 5 by 3, and get 15.
Then we multiply 2 by 7, and get 14.
Next we give both terms new denominators -- 7 × 3 = 21.
So now our fractions look like this:
15
21
−
14
21
Since our denominators match, we can subtract the numerators.
15 − 14 = 1
So the answer is:
1
-
21
or 1/21
