Ejercicio 4 (J-2005-2 UNED)

Dadas las matrices
$A = \left( \begin{array}{cc} 3 & 1 \\ 7 & 2 \end{array} \right) \qquad B = \left( \begin{array}{cc} 1 & -1 \\ 0 & 2 \end{array} \right)$
calcula