Percentages SAT question

The correct answer is $9.87$. It’s given that the number $a$ is $110\%$ greater than the number $b$. It follows that $a=(1+\frac{110}{100})b$, or $a=2.1b$. It’s also given that the number $b$ is $90\%$ less than $47$. It follows that $b=(1-\frac{90}{100})(47)$, or $b=0.1(47)$, which yields $b=4.7$. Substituting $4.7$ for $b$ in the equation $a=2.1b$ yields $a=2.1(4.7)$, which is equivalent to $a=9.87$. Therefore, the value of $a$ is $9.87$.