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What is 70/51 - 8/12?

What is 70/51 - 8/12?

Here's how to subtract 8/12 from 70/51:

70
51
8
12

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 70 by 12, and get 840.

Then we multiply 8 by 51, and get 408.

Next we give both terms new denominators -- 51 × 12 = 612.

So now our fractions look like this:

840
612
408
612

Step 2

Since our denominators match, we can subtract the numerators.

840 − 408 = 432

So the answer is:

432
612

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:

432
612
÷ 2 =
216
306

Let's try dividing by 2 again...

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

216
306
÷ 2 =
108
153

Let's try dividing by 2 again...

Nope! So now we try the next greatest prime number, 3...

Are both the numerator and the denominator evenly divisible by 3? Yes! So we reduce it:

108
153
÷ 3 =
36
51

Let's try dividing by 3 again...

Are both the numerator and the denominator evenly divisible by 3? Yes! So we reduce it:

36
51
÷ 3 =
12
17

Let's try dividing by 3 again...

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...

No good. 13 is larger than 12. So we're done reducing.

There you have it! The final answer is:
70
51
8
12
=
12
17