Chapter 3 - Solving Inequalities - 3-1 Inequalities and Their Graphs - Practice and Problem-Solving Exercises - Page 168: 36

$p\geq35$

A key phrase in writing this inequality is "at least 35 years old." This suggests that whoever is elected President of the United States can be 35, but no younger than 35. This translates to the greater than or equal to sign ($\geq$). Let $p$ represent the age of the President, where his age must be greater than or equal to 35. Therefore, this inequality is represented as $p\geq35$.