$5$: Calculate each person's average age of credit history. Round to the nearest tenth of a year:

$\backslash$table$[[$Name$,\backslash$table$[[$credit$],[$card $1]],\backslash$table$[[$credit$],[$card $2]],\backslash$table$[[$credit$],[$card $3]],\backslash$table$[[$average age of$],[$credit history$]]],[$Frank$,8$ years,$2$ years,none,$\frac{1}{2}=5$ years$],[$Gus$,13$ years,$5$ year,$1$ year,$6\mathrm{.}3$ vears$]]$