His son failed a math test. He got help from the most unexpected place.

Let's be real: Math is hard.

Yeah, I know some people love it. But for those who still struggle with figuring out percentages when it comes to leaving a tip, going back to elementary school mathematics (listen, I don't want to scare you, but have you thought about how terrifying long division is lately?) is enough to give you a headache.

You know what I have nightmares about? Those "three-minutes tests" I was given in third grade. The ones where I had to solve as many problems as I could in a limited time span. Those were the days my mom packed Mylanta with my lunch.

Everything is even harder when you're a parent.

You're an adult and out of school, and despite what your teachers said, you have a calculator at all times. You chuckle sensibly at "common core" memes (even though the system maybe makes sense). And then — you have a kid of your own. And that kid is struggling with math too.  Now it's your job to help them. What do you do?

That's the problem one dad faced recently. But he probably never expected find help on a subway train in Brooklyn. He was working on understanding fractions better so that he could come home and help his third-grader who'd failed a recent math test.

One commuter caught what happened next, and everyone's loving it.

According to Denise Wilson, who snapped a pic of Corey Simmons (he's the guy in red) and an unnamed good Samaritan (that's the guy in the hat), she was just trying to get home when she heard the two strangers having an intense conversation. About fractions.

“He was just telling the guy, ‘I’m in my 40s and all of this is new to me, so I’ve got to re-learn this to teach my son because he failed a math test,’” Wilson told CBS2.

This dad was in luck, though. The stranger had been a math teacher. And he had no problem stopping what he was doing to help the 42-year-old Simmons — who hadn't even thought about fractions in more than three decades — get back on the horse again.

“Everything he got wrong or was confused about, he broke it down and corrected him,” Wilson wrote in her post accompanying the image of the two men.

This reminder that people help each other in little ways every day is powerful.

Wilson says that Simmons and the math teacher got off at different stops. And even though Wilson's post has been shared over and over, no one's as of this story publication has figured out who the mysterious math teacher is. But perhaps that's the most beautiful part of this story: The guy wasn't helping for accolades or attention. He just saw another human being struggling, he had the expertise, and he offered to help.

Simmons may not be all the way up on fractions ("We're halfway there," he said), but the message he took home to his son that night was less about math than it was about perseverance — and never being afraid to ask for help. Even when that help comes from a place one may have never expected.

"You need help sometimes and you shouldn’t want to bite your tongue, to not ask for the help,” Simmons told CBS2. “So don’t feel shy to ask someone for help, it’s OK.”