The probability that a family owns a laptop is 0.68 ; that it also...

Let $L$ be the event that a family owns a laptop and $D$ be the event that a family owns a desktop.

Given:
$P(L) = 0.68$
$P(D) = 0.56$
$P(L \cap D) = 0.48$

The probability that a randomly selected family owns a laptop or a desktop is given by $P(L \cup D)$.

Using the addition theorem of probability:
$P(L \cup D) = P(L) + P(D) - P(L \cap D)$

Substituting the given values:
$P(L \cup D) = 0.68 + 0.56 - 0.48$

$P(L \cup D) = 1.24 - 0.48 = 0.76$