1000₂<x₁₀<10000₂ = 1,000,000<x₁₀<100,000,000 reading one million is less than x₁₀, and x₁₀ is less than 100,000,000.
Here is each answer for x₁₀:
7= 282,475,249
8= 1,073,741,824
15= 576,650,390,625
16= 1,099,511,627,776
With those numbers, it doesn't look like any answer is right. I am thinking I am not understanding the question....
