40 lightbulbs with 3 defective. What is probability that I will have 1 defective if I buy 20 lightbulbs?

twenty-six miles over two gallons because the proportion for the original 13 miles to one gallon would be written 13/1 and, doing the same thing to the top and bottom, i multiplied by 2 and got 26/2

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29 is x=.7

30 is y=3.375 or 3 and 3/8