9514 1404 393
Answer:
x = 4
Step-by-step explanation:
Maybe you want to find x such that ...
2/7 = x/(x +10)
2(x +10) = 7x . . . . . . multiply by 7(x+10)
20 = 5x . . . . . . . . . . subtract 2x, simplify
4 = x . . . . . . . . . . . . divide by 5
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<em>Additional comment</em>
You can almost solve this "by inspection" if you recognize the difference of the denominator and numerator is 5 on the left and 10 on the right. If you multiply the fraction on the left by 2/2, you get 4/14, the values in x/(x+10) in the fraction on the right.
Note that 60 minutes is 1 standard deviation away from the mean and from recalling the 68-95-99.7 rule, the area that will remain is (100 - 68) = 32%. However, we only want the leftmost portion of this area, so the answer is 32%/2 = 16%.
<span>Choose D.</span>
The answer would be approximately 1.98
