Jess puts 2 yellow counters and 1 blue counter in a bag. She then puts more blue counters in the bag.

She is going to take one counter without looking. The probability that the counter will be blue is $\frac{4}{5}$.
How many more blue counters did Jess put in the bag?

Answer

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Answer

$\boxed{7}$ more blue counters were added

Steps

Step 1 ：Set up the equation: $\frac{1 + x}{3 + x} = \frac{4}{5}$

Step 2 ：Solve for x: $x = 7$

Step 3 ：$\boxed{7}$ more blue counters were added