When i tried converting the mixed numbers into fractions and subtracting them I got 1 but 1 isn't one of the answer choices. What did I do wrong? The answer key reveal that it's C.
These are NOT mixed numbers. They are EXPONENTIAL numbers.
$\displaystyle \displaystyle \begin{align*} 2^{\frac{5}{2}} - 2^{\frac{3}{2}} &= 2\cdot 2^{\frac{3}{2}} - 2^{\frac{3}{2}} \\ &= 2^{\frac{3}{2}} \left( 2 - 1 \right) \\ &= 2^{\frac{3}{2}} \cdot 1 \\ &= 2^{\frac{3}{2}} \end{align*}$