TL;DR: The forever-useful Texas Instruments TI-84 Plus graphing calculator is on sale for $88 at Walmart, saving you $28. Since the dawn of time (okay, 1990), high school and college algebra classes ...

Add Yahoo as a preferred source to see more of our stories on Google. "Hearst Magazines and Yahoo may earn commission or revenue on some items through these links." If you're headed back to class next ...