““Mathematicians call it “the arithmetic of congruences.” You can think of it as clock arithmetic. Temporarily replace the 12 on a clock face with 0. The 12 hours of the clock now read 0, 1, 2, 3, … up to 11. If the time is eight o’clock, and you add 9 hours, what do you get? Well, you get five o’clock. So in this arithmetic, 8 + 9 = 5; or, as mathematicians say, 8 + 9 ≡ 5 (mod 12), pronounced “eight plus nine is congruent to five, modulo twelve.””
![“[On refusing to do nude movie scenes:] There are certain people who should know what you look like naked. I just don't think your high-school algebra teacher should be one of them.” quote by Julia Roberts](https://sms4smile.com/quotes/img-quotes/5cc/julia-roberts-2214_algebra_on-refusing-to-do-nude-movie-scenes-ther_58800.jpg)
