Subtract 18/21 from 30/42
30/42 - 18/21 is -1/7.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 42 and 21 is 42
Next, find the equivalent fraction of both fractional numbers with denominator 42 - For the 1st fraction, since 42 × 1 = 42,
30/42 = 30 × 1/42 × 1 = 30/42 - Likewise, for the 2nd fraction, since 21 × 2 = 42,
18/21 = 18 × 2/21 × 2 = 36/42 - Subtract the two like fractions:
30/42 - 36/42 = 30 - 36/42 = -6/42 - After reducing the fraction, the answer is -1/7
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