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It is almost embarrassing to ask this. But it has been awhile since I used math - but I got this homework problem , and I'm not sure if this refer to e power to the -1/18(x-5)^2 what exactly this {} bracket refer to ? is it a power of e( exponential ) ? I'm confuse and don't understand this ..

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    https://www.wolframalpha.com/input/?i=1%2F(3+Sqrt%5B2+Pi%5D)+Exp%5B-1%2F18+(x+-+5)%5E2%5D – 2017-02-12
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    http://lmgtfy.com/?q=exponential+function – 2017-02-12
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    This is the probability density function for a normal distribution with mean of `5` and standard deviation of `3` – 2017-02-12
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    It is simply $\text{exp}\{x\} = e^x$. The same written in a more fancy way. – 2017-02-12
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    The only time there could be a difference is when you look at $\exp(z)$ with $z$ a complex number. When we are not working in a context where complex numbers could appear, $\exp(x)$ is used as a synonym for $e^x$. – 2017-02-12

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Yes, $\exp(x)$ is identical to $e^x$. Therefore, your function can also be written as: $$h(X)=\frac{1}{3\sqrt{2}\pi}\cdot \exp{\left\{-\frac{1}{18}{(X-5)^2}\right\}}=\frac{1}{3\sqrt{2}\pi}\cdot e^{-\frac{1}{18}(X-5)^2}$$ This notation is preferred in some cases because some of the text may appear small or ambiguous when $e$ is used instead of $\exp$, especially when the exponentiated part is a fraction.