Subtract 18/21 from 15/18, Solve 15/18

Subtract 18/21 from 15/18

15/18 - 18/21 is -1/42.

Find the least common denominator or LCM of the two denominators:
LCM of 18 and 21 is 126

Next, find the equivalent fraction of both fractional numbers with denominator 126
For the 1st fraction, since 18 × 7 = 126,
15/18 = 15 × 7/18 × 7 = 105/126
Likewise, for the 2nd fraction, since 21 × 6 = 126,
18/21 = 18 × 6/21 × 6 = 108/126
Subtract the two like fractions:
105/126 - 108/126 = 105 - 108/126 = -3/126
After reducing the fraction, the answer is -1/42

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