Shelby mixes a 25% bleach solution with 5 cups of a 10% bleach solution, resulting in a 20% bleach solution. The table shows the amount of each solution used. Bleach Solution Cups Bleach Concentration Total 10 percent Bleach 5 0 point 1 0 0 point 5 25 percent Bleach x 0 point 2 5 0 point 2 5 x Mixture 5 plus x 0 point 2 0 3 What is the value of x ?

The 5 cups of 10% solution contain 5 × 0.10 = 0.5 cups of bleach, and x cups of 25% solution contain 0.25x cups. The mixture has 5 + x cups at 20%, so its bleach amount is 0.20(5 + x). Set the amounts equal: 0.5 + 0.25x = 0.20(5 + x), which gives 0.05x = 0.5 and x = 10. The correct choice is 10 cups.

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