Red balls

The bag has three red, 12 blue, and eight green balls. How many red balls must we add to the bag if we want the probability of pulling out the red balls to be 20%?

Correct answer:

n =  2

Step-by-step explanation:

(n+3)/(3+12+8+n)=20/100  (n+3)=0.20 (3+12+8+n)  0.8n=1.6  n=0.81.6=2  n=2

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