The number a is 70 % less than the positive number b . The number c

The correct answer is $.48$. It's given that the number $a$ is $70\%$ less than the positive number $b$. Therefore, $a=\left(1-\frac{70}{100}\right)b$, which is equivalent to $a=\left(1-0.70\right)b$, or $a=0.30b$. It's also given that the number $c$ is $60\%$ greater than $a$. Therefore, $c=\left(1+\frac{60}{100}\right)a$, which is equivalent to $c=\left(1+0.60\right)a$, or $c=1.60a$. Since $a=0.30b$, substituting $0.30b$ for $a$ in the equation $c=1.60a$ yields $c=1.60\left(0.30b\right)$, or $c=0.48b$. Thus, $c$ is $0.48$ times $b$. Note that .48 and 12/25 are examples of ways to enter a correct answer.