Help with this SAT Math question

Test Preparation
1

<p>I was doing a sample test in my sat study guide book, and I came across this question in mathematics that I just couldn't solve</p>

<p>I have the answer, I just need an explanation as to how it is solved
thanks</p>

<p>here's the question> </p>

<p>

<a href="http://i51.tinypic.com/oa3jo2.jpg%5B/IMG%5D"&gt;http://i51.tinypic.com/oa3jo2.jpg

</a></p>

2

<p>2^n + 2^ (n+1) = k
2^n (1+2) = k
3 x 2^n =k
2^n = k/3
4 x 2^n = 4k /3
2^2 x 2^n = 4k /3
2^(n+2) = 4k/3</p>