Here's how to subtract 4/10 from 2/7:
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 2 by 10, and get 20.
Then we multiply 4 by 7, and get 28.
Next we give both terms new denominators -- 7 × 10 = 70.
So now our fractions look like this:
Since our denominators match, we can subtract the numerators.
20 − 28 = -8
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...
Nope! So now we try the next greatest prime number, 3...
Nope! So now we try the next greatest prime number, 5...
No good. 5 is larger than -4. So we're done reducing.There you have it! The final answer is: