Calculate

$$
\frac{6 \cdot 5 \cdot 4 \cdot 3 \cdot 2 \cdot 1-5 \cdot 4 \cdot 3 \cdot 2 \cdot 1}{4 \cdot 3 \cdot 2 \cdot 1}
$$

Only a numerical answer is expected here.
By factoring the numerator by $4 \cdot 3 \cdot 2 \cdot 1$, the fraction becomes:

$$
\frac{4 \cdot 3 \cdot 2 \cdot 1 \cdot(6 \cdot 5-5)}{4 \cdot 3 \cdot 2 \cdot 1}=6 \cdot 5-5=25
$$

Remark: Generally, a number of the form $1 \cdot 2 \cdot \ldots \cdot(n-1) \cdot n$ is often denoted $n$! and called the factorial of the integer $n$.

Comment from the graders: The exercise was very well solved overall! However, several students tried to reduce the fraction without first factoring the numerator by 4! $(4 \cdot 3 \cdot 2 \cdot 1)$, and therefore did not find the solution.