2^{x }+ 2^{x+1}+ 2^{x+2}= 56

The solution is the following:

2^{x}+ 2 * 2^{x}+ 4 * 2^{x}= 56

Why is that? I don't understand how it came to this. Where did the 4 come from? How come there's so many 2s?

7 * 2^{x}= 56

2^{x}= 8

How did 56 turn into 8? Shouldn't it be 8^{2}instead of just 8?

2^{x}= 2^{3 }x = 3

I only understand the last two steps. Please help, I need to know this (and more) for a test. This isn't the only equation that confuses me, but it would help to know what lead to the final solution.

Please reply,

thanks.