Answers

Add 40/21 and 90/80

1^st number: 1 19/21, 2^nd number: 1 10/80

40/21 + 90/80 is 509/168.

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,
   40/21 = 40 × 80/21 × 80 = 3200/1680
3. Likewise, for the 2nd fraction, since 80 × 21 = 1680,
   90/80 = 90 × 21/80 × 21 = 1890/1680
4. Add the two like fractions:
   3200/1680 + 1890/1680 = 3200 + 1890/1680 = 5090/1680
5. 5090/1680 simplified gives 509/168
6. So, 40/21 + 90/80 = 509/168
   In mixed form: 35/168

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