On Behalf Of Erik Boling:
# humm ok so i tried out my *program* but at the very end i get 
# an error..
# irb(main):001:0> def ask(question)
# irb(main):002:1> puts "#{question}:\n"
# irb(main):003:1> gets.split
# irb(main):004:1> end
# => nil
# irb(main):005:0> Var_1 = ask("Enter 1st Vendors prices")
# Enter 1st Vendors prices:
# 14.50 16.50 14
# => ["14.50", "16.50", "14"]
# irb(main):006:0> Var_2 = ask("Enter 2nd vendors prices")
# Enter 2nd vendors prices:
# 13 17.50 14
# => ["13", "17.50", "14"]
# irb(main):007:0> Var_1.zip(Var_2)
# => [["14.50", "13"], ["16.50", "17.50"], ["14", "14"]]
# irb(main):008:0> Var_1.zip(Var_2).map{ |pair| pair[0] - pair[1] }
                                                    ^^^^       ^^^^
                                          try pair[0].to_f - pair[1].to_f
so,
irb(main):009:0> Var_1.zip(Var_2).map{ |pair| pair[0].to_f - pair[1].to_f }
=> [1.5, -1.0, 0.0]

# NoMethodError: undefined method `-' for "14.50":String
                                   ^^^            ^^^^^^
                                there's the hint 

# could it because im using floats, and not intergers?

you're using strings

kind regards -botp