To find out how much of the mountain Della climbs over the two days, we need to add the fractions she climbs each day.
On the first day, she climbs \( \frac{1}{4} \) of the mountain.
On the second day, she climbs \( \frac{2}{6} \) of the mountain.
First, we can simplify \( \frac{2}{6} \):
\[ \frac{2}{6} = \frac{1}{3} \]
Now we need to add \( \frac{1}{4} \) and \( \frac{1}{3} \). To do this, we need a common denominator. The least common multiple of 4 and 3 is 12.
Next, we convert both fractions to have a denominator of 12:
\[ \frac{1}{4} = \frac{1 \times 3}{4 \times 3} = \frac{3}{12} \]
\[ \frac{1}{3} = \frac{1 \times 4}{3 \times 4} = \frac{4}{12} \]
Now we can add the two fractions:
\[ \frac{3}{12} + \frac{4}{12} = \frac{3 + 4}{12} = \frac{7}{12} \]
So, the total amount of the mountain Della climbs over the two days is \( \frac{7}{12} \).