Chapter 2 - Equations, Inequalities, and Problem Solving - 2.3 Formulas - 2.3 Exercise Set - Page 101: 48

$s=2A-p-230$

Using the properties of equality, in terms of $ s $, the given equation, $ A=115+\dfrac{1}{2}(p+s) $, is equivalent to \begin{array}{l} 2(A)=2(115)+1(p+s) \\\\ 2A=230+p+s \\\\ 2A-230-p=s \\\\ s=2A-p-230 .\end{array}