if i buy 2 standard 80mm case fans how would i make one run slower than the other one ?

becuse i want one to be a intake fan and the other to be a egsored fan and ive herd that the egsored fan has to be working harder

just plug the fans in, you could use several things to limit the voltage from electronic supply stores, but why, if they were really meant to have faster/slower fans, they would make them and have them labled as 80mm intake, or 80mm egsored.