Answer
Since \$0.597/battery is less than \$0.624/battery, the single pack is the better buy.
Work Step by Step
If the battery in the single pack lasts 3 times as long, it is the equivalent of 3 batteries.
$\frac{1.79}{3 batteries}$ = $\frac{1.79\div3}{3\div3 batteries}$ = $\frac{0.597}{1 battery}$ = 0.597/battery
$\frac{4.99}{8 batteries}$ = $\frac{4.99\div8}{8\div8 batteries}$ = $\frac{4.99}{1 battery}$ = 0.624/battery
