Subtract 80/21 from 30/45, Solve 30/45

Subtract 80/21 from 30/45

1^st number: 30/45, 2^nd number: 3 17/21

30/45 - 80/21 is -22/7.

Find the least common denominator or LCM of the two denominators:
LCM of 45 and 21 is 315

Next, find the equivalent fraction of both fractional numbers with denominator 315
For the 1st fraction, since 45 × 7 = 315,
30/45 = 30 × 7/45 × 7 = 210/315
Likewise, for the 2nd fraction, since 21 × 15 = 315,
80/21 = 80 × 15/21 × 15 = 1200/315
Subtract the two like fractions:
210/315 - 1200/315 = 210 - 1200/315 = -990/315
After reducing the fraction, the answer is -22/7

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