Chapter 5 - Exponents and Polynomials - Chapters 1-5 Cumulative Review Problem Set - Page 234: 57

$x=40$

Let the unknown number be $x$. 15 percent of $x$ refers to the expression $(\frac{15}{100}\times x)$. Since fifteen percent of $x$ is 6, we obtain: Step 1: $(\frac{15}{100}\times x)=6$ Step 2: $15x=6\times100$ Step 3: $x=\frac{600}{15}=\frac{200}{5}=40$