Generate a random math question that always has a positive answer

random_math_question_positive_only.php

<?php

$ops = array('-', '+');
$answer = -1;
while($answer < 0 || $answer > 99) {
	$num1 = rand(0, 100);
	$num2 = rand(0, 100);

	$num1 -= 50;
	$num2 -= 50;

	shuffle($ops);
	$op = $ops[0];
	
	$answer = eval("return $num1 $op $num2;");
}

return "$num1 $op $num2 = $answer";

cool.