Subtract 45/42 from 12/90, Solve 12/90

Subtract 45/42 from 12/90

1^st number: 12/90, 2^nd number: 1 3/42

12/90 - 45/42 is -197/210.

Find the least common denominator or LCM of the two denominators:
LCM of 90 and 42 is 630

Next, find the equivalent fraction of both fractional numbers with denominator 630
For the 1st fraction, since 90 × 7 = 630,
12/90 = 12 × 7/90 × 7 = 84/630
Likewise, for the 2nd fraction, since 42 × 15 = 630,
45/42 = 45 × 15/42 × 15 = 675/630
Subtract the two like fractions:
84/630 - 675/630 = 84 - 675/630 = -591/630
After reducing the fraction, the answer is -197/210

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