Subtract 28/8 from 72/42, Solve 1 30/42

Subtract 28/8 from 72/42

1^st number: 1 30/42, 2^nd number: 3 4/8

72/42 - 28/8 is -25/14.

Find the least common denominator or LCM of the two denominators:
LCM of 42 and 8 is 168

Next, find the equivalent fraction of both fractional numbers with denominator 168
For the 1st fraction, since 42 × 4 = 168,
72/42 = 72 × 4/42 × 4 = 288/168
Likewise, for the 2nd fraction, since 8 × 21 = 168,
28/8 = 28 × 21/8 × 21 = 588/168
Subtract the two like fractions:
288/168 - 588/168 = 288 - 588/168 = -300/168
After reducing the fraction, the answer is -25/14

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