If you want to add or subtract fractions, what is the first thing you need to do?

take lowest common factor

Step-by-step explanation:

Find the least common denominator for both fractions and set up the fractions so they can both contain that same denominator.

Step-by-step explanation:

For example, let's say you want to add the fractions and .

First, you will want to find the least common demoninator.  Write out the multiples for both denominators originally given, in this case 4 and 7.  Let's go up to 4*10 and 7*10:

4: 4,8,12,16,20,24,28,32,36,40

7: 7,14,21,28,35,42,49,56,63,70

Se which number in both sets is the first number to be the same in both sets.  That will be your least common denominator.  In this case, the least comon denominator is 28.

To set the fractions right, you would need to multiply the first fraction, 3/4, by 7/7:

Then, you would need to multiply the second fraction, 2/7, by 4/4:

Now, since both fractions have a common deonminator now, you can add them togther and simplify afterwards if you need to:

And that's it.

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step-by-step explanation:

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