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### Course: 7th grade>Unit 4

Lesson 2: Adding & subtracting negative fractions

# Adding and subtracting fractions with negatives

Use the properties of addition to strategically add and subtract fractions with negatives and unlike denominators. We can rewrite the subtraction as adding the opposite so that the addition properties will apply. Created by Sal Khan.

## Want to join the conversation?

• I don’t get this, help!
(1 vote)
• Basically, we're trying to find out 3/7 - (-7/3)- 11/3
Something minus a negative is basically an addition problem. Ex. 2 - (-2) = 2+2=4.
He changed the minus negative to a plus.
3/7 + 7/3 - 11/3
He then turned it into this.
3/7 + 7+-11/3. The denominator will stay the same.
He then evaluated the problem.
Now we have 3/7 + -4/3
He then found the LCM, 21.
?/21 + ?/21
He evaluated the problem again.
9/21 + -28/21

Therefore,
3/7 - (-7/3)- 11/3 = -19/21

Hope this helped! Have a great rest of your day!
• how did you get the 11 from
• 11 was always part of the original problem.
(1 vote)
• Are you supposed to simplify the numbers or no?