Answers

Add 90/21 and 42/80

1^st number: 4 6/21, 2^nd number: 42/80

90/21 + 42/80 is 1347/280.

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,
   90/21 = 90 × 80/21 × 80 = 7200/1680
3. Likewise, for the 2nd fraction, since 80 × 21 = 1680,
   42/80 = 42 × 21/80 × 21 = 882/1680
4. Add the two like fractions:
   7200/1680 + 882/1680 = 7200 + 882/1680 = 8082/1680
5. 8082/1680 simplified gives 1347/280
6. So, 90/21 + 42/80 = 1347/280
   In mixed form: 4227/280

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