Here's how to subtract 9/10 from 7/8:
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 7 by 10, and get 70.
Then we multiply 9 by 8, and get 72.
Next we give both terms new denominators -- 8 × 10 = 80.
So now our fractions look like this:
Since our denominators match, we can subtract the numerators.
70 − 72 = -2
So the answer is:
Last of all, we need to simplify the fraction, if possible. Can it be reduced to a simpler fraction?
To find out, we try dividing it by 2...
Are both the numerator and the denominator evenly divisible by 2? Yes! So we reduce it:
Let's try dividing by 2 again...
No good. 2 is larger than -1. So we're done reducing.There you have it! The final answer is: