\[x - первое;(x + 10) - второе;\]
\[\left( \frac{x + 10}{2} \right) - третье.\]
\[x + x + 10 + \frac{x}{2} + 5 = 90\]
\[2,5x + 15 = 90\]
\[2,5x = 75\ \ \ \ \ \left| :2,5\ \right.\ \]
\[x = 30\ \ \ \ \ \ \ \ \]
\[30 + 10 = 40\ \ \ \ \ \ \ \]
\[\frac{40}{2} = 20\]
\[Ответ:30;40;20.\]