$\left( 20+7.5 \right)-{3}^{3}$
Evaluate the power$\left( 20+7.5 \right)-27$
Add the numbers$27.5-27$
Subtract the numbers$\begin{align*}&0.5 \\&\begin{array} { l }\begin{array} { l }\frac{ 1 }{ 2 },& 5 \times {10}^{-1}\end{array},& {2}^{-1}\end{array}\end{align*}$