What values do the elements $$a_{23}$$ and $$a_{12}$$ have in the matrix $$\left(\begin{array}{ccc} 42 & -13 & 0 \\ 31 & 12 & 8 \end{array} \right)$$

See development and solution

### Development:

The element $$a_{23}$$ corresponds to row $$2$$ and column $$3$$, it is therefore $$8$$.

The element $$a_{12}$$ corresponds to row $$1$$ and column $$2$$, it is therefore $$-13$$.

### Solution:

$$a_{23}=8$$ and $$a_{12}=-13$$.