Answers

Add 72/21 and 90/80

1^st number: 3 9/21, 2^nd number: 1 10/80

72/21 + 90/80 is 255/56.

Steps for adding fractions

1. Find the least common denominator or LCM of the two denominators:
   LCM of 21 and 80 is 1680
   
   Next, find the equivalent fraction of both fractional numbers with denominator 1680
2. For the 1st fraction, since 21 × 80 = 1680,
   72/21 = 72 × 80/21 × 80 = 5760/1680
3. Likewise, for the 2nd fraction, since 80 × 21 = 1680,
   90/80 = 90 × 21/80 × 21 = 1890/1680
4. Add the two like fractions:
   5760/1680 + 1890/1680 = 5760 + 1890/1680 = 7650/1680
5. 7650/1680 simplified gives 255/56
6. So, 72/21 + 90/80 = 255/56
   In mixed form: 431/56

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