math help

What is 20/64 - 8/10?

What is 20/64 - 8/10?

Here's how to subtract 8/10 from 20/64:

20
64
8
10

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 20 by 10, and get 200.

Then we multiply 8 by 64, and get 512.

Next we give both terms new denominators -- 64 × 10 = 640.

So now our fractions look like this:

200
640
512
640

Step 2

Since our denominators match, we can subtract the numerators.

200 − 512 = -312

So the answer is:

-312
640

Step 3

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:

-312
640
÷ 2 =
-156
320

Let's try dividing by 2 again...

Are both the numerator and the denominator evenly divisible by 2? Yes! So we reduce it:

-156
320
÷ 2 =
-78
160

Let's try dividing by 2 again...

Are both the numerator and the denominator evenly divisible by 2? Yes! So we reduce it:

-78
160
÷ 2 =
-39
80

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...

Nope! So now we try the next greatest prime number, 7...

Nope! So now we try the next greatest prime number, 11...

Nope! So now we try the next greatest prime number, 13...

Nope! So now we try the next greatest prime number, 17...

Nope! So now we try the next greatest prime number, 19...

Nope! So now we try the next greatest prime number, 23...

Nope! So now we try the next greatest prime number, 29...

Nope! So now we try the next greatest prime number, 31...

Nope! So now we try the next greatest prime number, 37...

Nope! So now we try the next greatest prime number, 41...

No good. 41 is larger than -39. So we're done reducing.

There you have it! The final answer is:
20
64
8
10
=
39
80