7 blue marbles because 3:7 equals red:blue so blue =7
The number of blue marbles that will be in the bag will be 7.
Let the number of blue marbles be represented by x.
From the information given, the equation to solve the question will be:
3/7 = 3/x
Cross multiply
(3 × x) = 7 × 3
3x = 21
Divide both side by 3
3x/3 = 21/3
x = 7
Therefore, the correct option is 7 blue marbles.
Learn more about ratio on:
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