First, find the base rate of both of the numerals, to do this simply divide the price by the number of units.
12.95 divided by 3 is 4.32 ( rounded to nearest cent )
21.45 divided by 5 is 4.29 ( rounded to nearest cent )
So, if you want the better deal ( which is what I've interpreted ), then 5 pounds of nuts is the better deal BY 3 cents.
Hope this helps, if not, comment below please!!!!