<?php
$strength = "50";
$weapon_power = "60";
$max_damage = $strength+$weapon_power/10;
$attack ="50";
$defense = "50";
$hp = $defense+$strength+$attack/3;
echo "Str: <b>$strength <br></b>";
echo "Weapon Power:<B>$weapon_power</b> <br>";
echo "Max Dmg: <b>$max_damage</b> <br>";
echo "attack: <b>$attack</b> <br>";
echo "def: <b>$defense</b> <br>";
echo "HP: <b>$hp</b><br>";
?>
if you put quotes arround your equation, its gonna print the literal meaning. it wasnt parsing the +'s through php basically, so it just displayed them.