Let \( x \) be the amount of cat food Kendall gives in the morning and afternoon combined. According to the problem, we have the equation:
\[ x + \frac{1}{2} = \frac{4}{5} \]
To solve for \( x \), first, we need to isolate \( x \):
\[ x = \frac{4}{5} - \frac{1}{2} \]
To perform this subtraction, we need a common denominator. The least common denominator of 5 and 2 is 10.
Convert \( \frac{4}{5} \) and \( \frac{1}{2} \) to tenths:
\[ \frac{4}{5} = \frac{4 \times 2}{5 \times 2} = \frac{8}{10} \] \[ \frac{1}{2} = \frac{1 \times 5}{2 \times 5} = \frac{5}{10} \]
Now substitute these values back into the equation:
\[ x = \frac{8}{10} - \frac{5}{10} \] \[ x = \frac{3}{10} \]
Thus, Kendall gives her cat \( \frac{3}{10} \) cup of food the rest of the day.