Answers

Subtract 70/80 from 20/42

20/42 - 70/80 is -67/168.

Steps for subtracting fractions

1. Find the least common denominator or LCM of the two denominators:
   LCM of 42 and 80 is 1680
   
   Next, find the equivalent fraction of both fractional numbers with denominator 1680
2. For the 1st fraction, since 42 × 40 = 1680,
   20/42 = 20 × 40/42 × 40 = 800/1680
3. Likewise, for the 2nd fraction, since 80 × 21 = 1680,
   70/80 = 70 × 21/80 × 21 = 1470/1680
4. Subtract the two like fractions:
   800/1680 - 1470/1680 = 800 - 1470/1680 = -670/1680
5. After reducing the fraction, the answer is -67/168

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