Example

Simplifying 38+(58)18\frac{3}{8} + \left(-\frac{5}{8}\right) - \frac{1}{8}

Combine three fractions that all share the denominator 88, involving both addition and subtraction with a negative fraction in parentheses:

38+(58)18\frac{3}{8} + \left(-\frac{5}{8}\right) - \frac{1}{8}

Because the denominators are identical, write all three numerators over the common denominator:

3+(5)18\frac{3 + (-5) - 1}{8}

Evaluate the numerator from left to right. First, 3+(5)=23 + (-5) = -2, giving 218\frac{-2 - 1}{8}. Then 21=3-2 - 1 = -3, so the fraction becomes 38\frac{-3}{8}. Rewrite with the negative sign in front of the fraction:

38-\frac{3}{8}

This example extends the common-denominator rule to an expression with three fractions and a mix of addition and subtraction. The same strategy applies: place all numerators over the shared denominator and simplify the resulting integer arithmetic step by step, working left to right.

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Updated 2026-04-21

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