1. Convert this into their respective z values.

z = \frac{x - \mu}{\sigma}

Then work out the areas using your normal table. Tell us what you get!

Note: Making a simple sketch sometimes gets you the correct answer faster and makes sure you have got it.

2. This can be done by looking at your table itself and do the necessary arithmetic.

By the way, N(100, 15) happens to be the distribution of IQ (Intelligence Quotient) (http://en.wikipedia.org/wiki/Iq).

http://en.wikipedia.org/wiki/File:IQ_curve.svg