The shirt reads: “THERE’S A FINE LINE BETWEEN A NUMERATOR AND DENOMINATOR — ONLY A FRACTION OF PEOPLE WILL FIND THIS FUNNY.”
The two key words are stacked with a horizontal rule between them, so the layout itself forms a fraction.
The line between them is literal and it is right there on the shirt. The second half is the shirt anticipating its own reception, which is fair.
For maths teachers, for anyone who has told this one to a classroom, and for a joke that is funnier for admitting its limits.
