Adding & Subtracting FractionsATI TEAS 7 cheat sheet

Common denominator first

10 key facts 3 practice questions Reviewed Oct 2026

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The Rule

You can only add or subtract with a common denominator
Find the LCD (least common denominator)
Convert each fraction, then add or subtract numerators only
Denominator does not change

Worked

1/4 + 2/3 → LCD 12
= 3/12 + 8/12 = 11/12
5/6 − 1/2 → LCD 6 = 5/6 − 3/6 = 2/6 = 1/3

Mixed Numbers

Convert to improper fractions first, or add whole parts separately
Borrow from the whole number when the top fraction is smaller

Always

Simplify the answer — divide top and bottom by their GCF

Key takeaway

Common denominator first

Before you read

Test yourself first: 3 questions

Question 1 of 3

What is 7 − (−3)?

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