I'm willing to accept someone was careless if they mix up rise/run or run/rise. But you can readily summon the correct expression if you understand what slope m

I'm willing to accept someone was careless if they mix up rise/run or run/rise. But you can readily summon the correct expression if you understand what slope means algebraically/geometrically. So barring a sloppy mistake, which we all have, it's just as indicative of lacking proper geometric understanding. For example, a basic linear equation y = m*x would readily yield that m being the slope is m = y/x, so it's rise over run. That's one of the things I always treasured about math, that you could work out the formulas if you didn't care to memorize them.