If there is one donut on the sidewalk and Theo eats it, how many donuts are on the sidewalk?

Yesterday at work somebody tried to pay for a $56 session by handing me three twenties, a five and a single. I looked in my drawer to see if I had a ten dollar bill to give as change, but all I had was a five and three singles.

"I'm sorry, all I have is a five and three singles." I say to the nice man.

"That's ok. Just give me back my five." He says.

"... What?"

"I thought you might have a ten, but you don't, so just give me my five and your five."

I look down at the money in my hands. "Um... but... that's not right. I will still have three twenties. That's not enough change."

He cocks his head to his left shoulder and studies me for a moment. "Yes it is."

"No, no, it can't be. I'll still have three twenties."

"Right, but you'll have given me correct change."

I look down at the money again. A line is starting to form behind the nice man waiting for his change. I spread the bills across my desk. Three twenties, a five and a single, plus the five from my cash drawer. Seventy-one dollars. If I give him five back, that's .... what is that? I put my five back in my drawer and start over. The line is growing restless. I can hear people tapping their feet impatiently, sighing heavily, coughing. My palms begin to sweat. I take a deep breath. Three twenties, a five and a single. Sixty-six dollars. Take away his five. Now I have sixty-one. I take the five from my drawer and put it with his five. I still have sixty-one dollars in front of me. How could I still have sixty-one dollars?

"Just pretend I gave you sixty-one instead of sixty-six." he says, trying to be helpful.

My vision starts to go black around the edges and I can hear my own pulse. I laugh, nervously. "I don't understand. I ... um .... sixty-six minus five is sixty-one minus five is - " I CAN'T REMEMBER WHAT SIXTY-ONE MINUS FIVE IS. 

"Fifty-six."

"It is?"

"Yes."

"Um...."

"That's the correct change."

"Then why do I still have three twenties?" I'm pretty sure the look on my face is what Michael would call 'Valley Girl Vacant'.

"Would you like me to just pay with a credit card?" Sweet, kind, patient man.

"No! No. I can figure this out." I grab a pen and write down 61 - 5 =

I got nothin'.      

61 - 5 =

FUCK.

61 - 5 =

And then I count on my fingers for the answer. 

61 - 5 = 56. 

I stare at the equation. I look at the bills on my desk. There are three twenties and a single. Sixty-one dollars. There should only be fifty-six dollars. WHY ARE THERE STILL SIXTY-ONE DOLLARS?

I don't know what that sweet man thought of me, but he should get a special place in heaven for being so patient. Ultimately I figured it out, but it took him and two other people to explain to me HOW MAKING CHANGE WORKS. There is a reason I am an actor and not, say, a veterinarian. Can you imagine me with a scalpel and my nerves, trying to perform surgery on some poor animal? You'd bring your dog in to be neutered and you'd get him back with a second butt hole.