1. The problem asks to translate the verbal phrase "One-fourth times a number n, minus thirty" into a mathematical expression. 2. "One-fourth times a number n" means multiply $\frac{1}{4}$ by $n$, which is written as $\frac{1}{4}n$. 3. "Minus thirty" means subtract 30 from the previous result. 4. Putting it all together, the expression is: $$\frac{1}{4}n - 30$$ This expression represents one-fourth of $n$ minus thirty.