Answer
A higher life expectancy might mean better per capita income, which might imply more personal computers per capita.
Work Step by Step
Life expectancy, per capita income and number of personal computers are connected in the following way:
Per capita income $\rightarrow$ Life expectancy
Per capita income $\rightarrow$ Number of personal computers per capita
When Per capita income increases, so does Life expectancy (due to more possibilities for medical care), so Per capita income and Life expectancy have a positive correlation.
When Per capita income increases, so does Number of personal computers per capita (due to the fact that people are richer), so Per capita income and Number of personal computers per capita have a positive correlation too.
The reason why a positive correlation might exist between Life expectancy and Numbers of computers per capita is the fact that a higher life expectancy might mean better per capita income, which might imply more personal computers per capita.
