Math question help me please

<p>in 10 RS, page 528, section 1, number 25 (last one)...</p>

<p>i've been stuck on this problem for about 20 minutes and i can't figure it out. could someone tell me how they did it?</p>

<p>I don't really want to find my book, so go here</p>

<p><a href=""&gt;;/a&gt;&lt;/p>

<p>It'll save you time in the long run anyway ;)</p>