He stuffed an enormous piece of Turkish delight in his mouth and began to chew slowly and deliberately, with a strange gleam in his eyes.

“Multiplying out what?” I asked.

“Well, the brackets of course. What else would you want to multiply out?”

“I don’t understand.”

“Right. You cross out the brackets and that gives you: x – 8x – 2 = 8 – 4x + 2. See?”

“Then what do I do? That’s not all, is it?”

“Of course not, you dope. Then you put all the xs on the left and everything else on the right. And don’t forget to swap the plus signs to minus when they switch sides.”

“OK, so that makes… that makes… x – 8x + 4x = 8 + 2 + 2.”

“And there you are. So now what do we do?”

“I don’t know, maybe we could go and kick a ball around!”

He nearly choked on his Turkish delight. There was icing sugar coming out through his eyes: they looked like two little snowballs.

“No, you birdbrain, you haven’t finished it. You’ve got to find the value of x!”

I felt tears come into my eyes. I thought of Dad, who had given me The Three Musketeers, who had done super well at school when he was young, who’d had his ear chewed off by Lucky Luke and who did everything, pretty much, to keep tabs on me … and here I was, KO’d by the first x of the year.

“Right,” Haisam resumed calmly. “You need to simplify. So simplify.”

“OK, I’m simplifying, I’m simplifying. I’ll simplify until it’s simply fizzing. Here we are, I get: – 3x = 12.”

“And now you just need to divide by 3!”

“Obviously… Whew! But it looks a bit weird to me: x = 12 ÷ – 3… I must have slipped up somewhere…”

“No, it’s right, it means x = – 4. Do you get it now?”

“To be honest, I don’t really see the point of it, but I get it. Though I don’t know if I’ll be able to do it again on my own. I can’t promise.”

“I can’t think how you’re going to manage an equation with several unknowns,” he said, guzzling another piece of Turkish delight.

“Is there such a thing?”

“In maths, everything’s possible.”

“How come you learnt all this?”

“It’s different for me. I can’t claim any credit for myself: Egyptians have always been great mathematicians.”

“What about Turks who observe the Sabbath?”

“Turks too. Even those who don’t observe the Sabbath.”