Answer:
144 marbles show some blue
Explanation:
You want to know the number of Mia's marbles that show some blue if 2/3 show some red, 3/4 show some yellow, and 6/7 show some blue.
Marbles
In order for the number of marbles, and each of the fractions, to be integers, the number of marbles must be a multiple of 3, 4, and 7. The smallest such multiple is 84. The largest that is less than 250 is 2·84 = 168.
Assuming Mia has 168 marbles, the number showing some blue is ...
168 · 6/7 = 144
144 of Mia's marbles show some blue.
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Additional comment
The ratios of colors showing must be ...
red : yellow : blue = 56 : 63 : 72
of a group of 84 marbles. Above, we have assumed there are two such groups.
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