Subtract 30/8 from 7/21, Solve 7/21

Subtract 30/8 from 7/21

1^st number: 7/21, 2^nd number: 3 6/8

7/21 - 30/8 is -41/12.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 8 is 168

Next, find the equivalent fraction of both fractional numbers with denominator 168
For the 1st fraction, since 21 × 8 = 168,
7/21 = 7 × 8/21 × 8 = 56/168
Likewise, for the 2nd fraction, since 8 × 21 = 168,
30/8 = 30 × 21/8 × 21 = 630/168
Subtract the two like fractions:
56/168 - 630/168 = 56 - 630/168 = -574/168
After reducing the fraction, the answer is -41/12

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