1) In this question, we need to make use of a standard normal table to check which is the value (in terms of Z-score) for that 10%.
2) Checking that out, we can see that the Z-score is -1.282. So now, let's plug that into the Z-score formula so that we get the corresponding raw value:
[tex]\begin{gathered} Z=\frac{X-\mu}{\sigma} \\ -1.282=\frac{X-3.5}{0.6} \\ X=2.73\approx2.7 \end{gathered}[/tex]Thus, this is the answer: 2.7 years
