This question is essentially about prime-factorization, but you can actually avoid some of the work if you're comfortable with basic division.
We're told to make IDENTICAL bouquets using 21 white and 91 red tulips AND we're told that NO flowers are to be left out.
With 21 white tulips, there are only three ways to form identical bouquets:
21 bouquets with 1 white flower each
7 bouquets with 3 white flowers each
3 bouquets with 7 white flowers each
With 91 red tulips, we just have to see which of those options divides into 91...
21 does NOT divide evenly into 91
7 DOES divide evenly (13 times)
3 does NOT divide evenly into 91
We're asked to find the GREATEST number of possible bouquets that can be formed, but since we're making multiple bouquets, there's only one answer that fits.
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