Consider the following system of linear equations $$$\left[ {\matrix{ 2 & 1 & { - 4} \cr 4 & 3 & { - 12} \cr 1 & 2 & { - 8} \cr } } \right]\left[ {\matrix{ x \cr y \cr z \cr } } \right] = \left[ {\matrix{ \alpha \cr 5 \cr 7 \cr } } \right]$$$

Notice that the second and the third columns of the coefficient matrix are linearly dependent. For how many values of $$\alpha $$, does this system of equations have infinitely many solutions?

Let $$G$$ be an arbitrary graph with $$n$$ nodes and $$k$$ components. If a vertex is removed from $$G$$, the number of components in the resultant graph must necessarily lie between

$$m$$ identical balls are to be placed in $$n$$ distinct bags. You are given that $$m \ge kn$$, where $$k$$ is a natural number $$ \ge 1$$. In how many ways can the balls be placed in the bags if each bag must contain at least $$k$$ balls?

$$n$$ couples are invited to a party with the condition that every husband should be accompanied by his wife. However, a wife need not be accompanied by her husband. The number of different gatherings possible at the party is