1/2 -1/1

To solve the expression \( \frac{1}{2} - \frac{1}{1} \):

1. Convert \( \frac{1}{1} \) to a fraction with the same denominator as \( \frac{1}{2} \). Since \( \frac{1}{1} = \frac{2}{2} \):

   \[ \frac{1}{2} - \frac{2}{2} \]

2. Now, subtract the two fractions:

   \[ \frac{1 - 2}{2} = \frac{-1}{2} \]

Therefore, \( \frac{1}{2} - \frac{1}{1} = -\frac{1}{2} \).