Answers

Add 21/12 and 90/80

1^st number: 1 9/12, 2^nd number: 1 10/80

21/12 + 90/80 is 23/8.

Steps for adding fractions

1. Find the least common denominator or LCM of the two denominators:
   LCM of 12 and 80 is 240
   
   Next, find the equivalent fraction of both fractional numbers with denominator 240
2. For the 1st fraction, since 12 × 20 = 240,
   21/12 = 21 × 20/12 × 20 = 420/240
3. Likewise, for the 2nd fraction, since 80 × 3 = 240,
   90/80 = 90 × 3/80 × 3 = 270/240
4. Add the two like fractions:
   420/240 + 270/240 = 420 + 270/240 = 690/240
5. 690/240 simplified gives 23/8
6. So, 21/12 + 90/80 = 23/8
   In mixed form: 27/8

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