I got this problem from a guide book.

Question:

It is given that $\displaystyle -5\le p\le 2$ and $\displaystyle 3\le q \le 10$.

Find the least posible value of $\displaystyle \frac{q-p}{q}$

Answer given in the book is as follows:

Least possible value $\displaystyle \frac{q-p}{q}=\frac{3-2}{10}=\frac{1}{10}$

My question is how can the variableqtakes two different values in an algebraic expression.

Please help.

Thanks.