It seems to be reading the input as blank before the user even enters the answe
Your code is not giving the user a chance to enter the number that will be saved in $response1, then, your comparisons operators are those used for strings and not for numbers, and above all, you missed important warnings by not useing strict and warnings, here is your code retouched.... 
#!/usr/local/bin/perl
use strict;
use warnings;

print "Content-type: text/html\n\n";
use CGI qw(:standard);

my $cornplanted=0;
my $cornnotplanted=0;

#@number1=("12" .. "25");
#$number1rand=$number1[rand @number1];
my $number1rand=int(rand(20));
my $number2=int(rand(12));

my $correctanswer=($number1rand + $number2);

print "$correctanswer <br>";

my $output=<<_html_;

<html>
<body>
<form method="post" action="foodaddition.cgi" name="form2">
Crops planted: $cornplanted <br>
<input type="hidden" name="$cornplanted" id="$cornplanted" />
Crops not planted: $cornnotplanted <br>
<input type="hidden" name="$cornnotplanted" id="$cornnotplanted" />
What does this math problem equal? <br>
$number1rand + $number2 = <input type="text" name="response1" id="resp
+onse1" />
<input type="hidden" name="response1" id="response1" />
<input type="submit" name="submit" value="Submit" />
</form>
</body>
</html>

_html_
print $output;

chomp(my $response1 = <STDIN>);
if ($response1  == $correctanswer)
{
    $cornplanted=($cornplanted + 1);
    print "correct!";

}

elsif ($response1 != $correctanswer)
{
    $cornnotplanted=($cornnotplanted + 1);
    print "not correct!";

}

[download]
An interesting question, what if you wanted your program to respond to a non-conforming user entry (i.e when a user enters a sentence rather than a number)? Scalar::Util has an answer for you :)

Excellence is an Endeavor of Persistence. A Year-Old Monk :D .

In reply to Re: having trouble with simple math game by biohisham
in thread having trouble with simple math game by mynameisG

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